EDIT: Please move discussion to Character Customization - We want more! - I did not see a thread was made before I made this thread.
I have added this post as a reply in that thread.
Summary
To preface, I had help compiling this thread, as I didn’t want to leave anyone out. If we somehow forgot a popular request, feel free to let me know and I can add it. Also, if any artists have an issue with me reposting their concept art here, just let me know, you can link this thread to ping me in General Discussion. Same with if you know who it came from, I can add credit. 
(I can also remove the images if the artist doesnt want it up)
Anyway, customization was one of the main selling points of Shadowlands, and when we were told there would be no more added, it was a massive letdown and had tons of threads about it. Then you announced in 9.1.5 that 3 allied races were being updated, which was great.
So please don’t let the customization options stop, they’re arguably the one thing most players agree on being a good thing being added. Here’s a list of the customization options players have been asking for, summed up.
Pandaren:
- Jewelry: Jade. Large Wooden Beads. Celestial-Focused Jewelry (Black Ox, White Tiger, Green Dragon, Red Crane). Koi Fish. Turtles. Pawprints.
- More Face Options (Female have a perpetual :3 face with no way to opt out)
- Scars
- Blind Eye Options
- Longer Beards for Males
- Eyebrow Customization
- More Hairstyles (with Headbands and such)
- Ability to remove the “Naked” Sandals
- Faction-Based Jewelry, Tattoos, etc. to help create some Faction Pride for Pandaren
- Tail Options for Male Pandaren
Draenei:
- More Eye Colors (E.G. Green, Purple)
- More Horn Options
- More Face Options
- Red/Dark Purple Skin Option
- Scars
- Tattoos (Red, Green, Black, etc.)
Note: The Skin and Tattoo options will help facilitate the Man’ari fantasy. Lore-wise, it’d be rather easy for them to explain that some Man’ari sought forgiveness from Velen after Sargeras’s defeat. Yes, they committed horrible atrocities, but so did the Death Knights. This will also give a choice that isn’t the bland white/blue skin tones Draenei currently have.
Concept Art (as a Horde Allied Race, but still works here) by Rurukatt:
https://pbs.twimg.com/media/DBGaVMRXUAEy6Nx.jpg
Trolls and Zandalari Trolls:
- Beards
- Scars
- More Jewelry, inspired by the Zandalari NPCs like Priestess Alun’za
- More Eye Colors
- More Tusk Customization
- Forest and Ice Troll Skin Options
Beard Mockup by RamavataramaArt, Unsure about Tattoo/Tusk/etc. Mockup Artist:
https://cdn.discordapp.com/attachments/609212795522777089/967520049973850232/unknown.png
https://cdn.discordapp.com/attachments/609212795522777089/967165104707747940/unknown.png
Worgen:
- Tails (Arguably the most requested feature of any race on the forums)
- Mane Colors
- Hair Accessories (Hat, Roses, etc.)
- Night Elf “Two Forms” Option.
- More Face Options
- Scars
Orcs and Mag’Har Orcs:
- Blackrock, Dragonmaw and Fel Orc Skin Options.
- Dragonmaw Tattoos.
- Bleeding Hollow Eye options.
- Shattered Hand Stump.
- Eyebrow Options.
Goblins:
- New Hairstyles
- Younger Faces
- More Jewelry
- Tattoos
- Gilgoblin Skin/Hair Options
Face Concept Art by Faebelina, Hairstyle/etc. by Ray of the Sun.
https://cdn.discordapp.com/attachments/609212795522777089/967521048620826715/unknown.png
https://cdn.discordapp.com/attachments/609212795522777089/967170861616492544/unknown.png
Vulpera:
- Actual Hair/Hairstyles
- More Fur Colors
- More Ear Shapes
- More Mouth Shapes
- Scars
- Different Fur Types (Shaggy, Fluffy, etc.)
- More Eye Colors, Maybe Heterochromatic Options (Like Most Core Races Received)
- More Varied Patterns
- More Jewelry Options
Lightforged Draenei
- Darker Skin Tone Options
Note: It’s understood Lightforged are supposed to have light skin, however, Lightforged Death Knights exist, so having a Darker Skin Tone for them would be nice, and having it available in general would be great. Onyx Skin Mockup by Somand.
https://i.imgur.com/TegWg4v.png
Mechagnomes
- More Metallic Color Options (Saronite, Fel Iron, etc.)
- Mismatched Limb Colors/Types
- More Hand Options (Thicker, Thinner, Tesla Coil, Buzz Saw, Cannon, etc.)
- Titanic Mechagnome Options for Head/Appendages
- The Ability to be 100% Robotic
- Non-Bipedal Legs (Mechaspider, etc.)
- Borg-Like Mecha-Implants (Mecha Parts on Cheek, Eyebrows, etc.)
- More Eye Customization (Different Colors, One Mecha, One Bio, Flashlights, etc.)
- Separate Ear, Chin, and Eye Modifications so they can be Mix/Matched
- Mecha-Mouth Option
- More Varied Hair Colors (Brighter, similar to Gnomes)
- More Hair Styles
- Cybernetic Hair (LED Lights, etc.)
- Scars (Grease/Burn Marks, Damaged Limbs, etc.)
- Tattoos
All images from The Mechagnome Megathread linked at the bottom.
https://cdn.discordapp.com/attachments/906673083560120330/927391671266725929/eyecolormechagnome.png
https://cdn.discordapp.com/attachments/906673083560120330/927391467813613629/Headpeices.png
Forsaken
- Upright Posture Option
- “Stitched” Skin Option
- Facial Hair
Humans
- Tattoos
- Asymmetrical Earrings
- Remove Some Faces Being Locked Behind Skin Color
Night Elves
- Jewelry Option For Males
- More Headdresses
- More Varied Markings
- More Earrings
- “Neutral” Faces for Males
- Fix “Disappearing Eyebrows” with Certain Helms, like the Halloween Hats
Zandalari Trolls
- More Hair Styles/Colors
- New Eye Colors
- More Tattoos
Kul Tiran
- Tattoos (Sailor/Shipfarer Tattoos)
- More Beard Options
Mag’har Orcs
- More Hairstyles
- More Eye Colors
Dark Iron Dwarf
- More Hair Styles/Colors
- More Eye Colors
- More Tattoos
- Jewelry
Tauren
- Grimtotem Skin Options
- Other Tribe (such as Grimtotem) Face Paint Options
- More headdresses
Nightborne
- Better Shaped Eyelashes
- Fix the Mis-Aligned Hairstyles (Explanations in this thread.)
- More Headdress Styles
- Better Placement for Hair Decorations on some Hairstyles
- Higher Definition Jewelry that fits the Nightborne Theme, not Night Elf Like Current.
- “Neutral” Faces for Males
- Fix “Disappearing Eyebrows” with Certain Helms, like the Halloween Hats
- Fix the Chin Decorations and Heritage Armor Chestpiece Confliction
- Better Luminous Hands Animation
- More Visible Tattoos
- Fix the Choppy Edges on Tattoos
Blood elves:
- Scars
- Farstrider Tattoos (Various Colors)
- Farstrider Feathers
- Rune “Tattoos”, Similar to those seen in the BC Art
- Amber, Orange, Black, and Red Eyes Option (the latter two for Dark Ranger/Darkfallen Fantasy (Including Optional Around-the-Eye Markings)
- Heterochromia Eye Options
- More Blind Eye Options
- Eyebrow Size Options
- Darkfallen Skin Tone Options
- San’layn Bat-Style Ear Options
- Fangs and Claws for Darkfallen Fantasy
- Phoenix/Light based Tattoos
- Golden Hair Highlights for a more Light Based Paladin Theme
- Phoenix-style weapons
- Male Jewelry & Jewelry Removed from Original Update
- An Updated Paladin Mount, either a Hawkstrider, to show their growth on their own, or an updated Courser.
Note: Most San’layn desiring players want them as an Allied Race. However, if you don’t plan to add them as one, I imagine (I can’t speak for them) they’d rather customization than not at all. (I highly recommend reading the Megathread: San’layn/vampyr elf Customization (and Allied Race idea) Coagulated Megathread {Re-VAMPed} - It’s by far one of the biggest threads in the forum, outlines hair styles, hair colors, ear options, etc. I can’t really summarize everything in this.)
“Rune Tattoo” art by Unknown. San’layn Art by ZombieQualia on Twitter. Farstrider Tattoo Mockup by Somand. Phoenix/Light Tattoo by Ace. Phoenix Weapons by Olivia Leppard.
https://i.redd.it/sp9funq2bil51.png
https://i.imgur.com/72oZ2Ty.png
https://i.imgur.com/lpEFjjA.png
https://i.imgur.com/1WIMMS6.png
https://i.imgur.com/S9S41tf.png
https://cdn.discordapp.com/attachments/609212795522777089/967166534885703740/unknown.png
https://cdn.discordapp.com/attachments/906672614490128414/926871661330960404/20220101_080755.jpg
Void Elves:
- More Hairstyles, with Tentacle Toggles
- Void / Starcursed Hair Effects
- Jet Black and Stark White Hair Colors
- Tattoos (Purple, Black, Silver, Dark Blue)
- Eyebrow Size Options
- Scars
- More Jewelry Options for Both Genders
- Black/Greyish/Void Skin Tones
- Entropic Embrace Toggle
- Void Corrupted “Normal” Skin Tones
- More Eye Colors (Greys, Blacks, Pinks, maybe Old God Inspired Eyes)
- More Hair Colors (Pinks, Purples, Greys)
- More Tentacle Color Options (Starcursed Blue, Black, Fuchsia and White)
- Fix Receding Hairlines and Holes Caused by Tentacle Toggle
- Remove Some Faces Being Locked Behind Skin Color
Female Hairstyles by Faebelina, Male by Luoren, Starcursed Hair by Rama, Eye Options by Silverleaf, Skin Tones by Silverleaf, Hair Colors and Void Corrupted Normal Skin tones and Scar Mockups by Ramavatarama. Non-Void Hairstyles by Rama. Nightborne/Void Elf Hairstyles by Faebelina.
https://cdn.discordapp.com/attachments/609212795522777089/967167934596259930/unknown.png
https://cdn.discordapp.com/attachments/609212795522777089/967520969944105000/unknown.png
https://cdn.discordapp.com/attachments/609212795522777089/967520652510785637/unknown.png
https://i.imgur.com/zPRLe9w.png
https://cdn.discordapp.com/attachments/906672592189022268/961740581816631336/20220407_141923.jpg
https://pbs.twimg.com/media/EWJf0RuXsAAcjwe.jpg
(The top hairstyles are Nightborne)
https://cdn.discordapp.com/attachments/966474522280742922/967436346480287754/5caec8c222b9a292e842ff07a7389c79.png
I apologize if I missed anyone. Feel free to ping me if I did, as I said. I tried my best to get all of the popular requests.
Here is the mega-thread of customization threads that go into more detail, with more concept art, of pretty much everything here:
Index/Compilation of Amazing Customization Suggestions Threads
Some Megathreads not listed in that:
High Elf Allied Race Megathread (Continuation)
Void Elf Customization Thread (For The Void Aspect)