There’s somethings that I feel conflict with lore and that’s what vexes me. If they provided simple reasons to how it fits though; I’d be fine / wouldn’t care less.
Humans is fine, I mean they descended from Vrykul who came from the Titanforged and they had different variants (Elemental colours etc) of them; so it makes sense and would actually be more lore accurate that there’s more diversity among that race.
Blue Pandas is odd, and I dunno how that fits but I’m sure they could use arcane radiation over the pass few expansions since MoP to reflect that.
Blood Elves was complex because they were defined as a evolved from a darker toned to a more fairskinned and shorter race; but if you know where to look you can find justifaction for it which I included in a thread of mine: The Customisation Justifications to Lore
People had the same conflict with Night Elves with Blonde hair, but one could wager that since the Cataclysm having the Highborne rejoin the Nightelves + the Alliance there could had been some Highborne that were of the Sunstrider house whom did not travel with the head of their house + followers when they ventured to discover Quel’Thalas.
Ultimately though, with the Goblins and Gnomes technology I don’t see how Tattoos & Hair Colour should be too much to fuss about.
As for other potential customisations; Blizzard said at Blizzcon they’ll also be looking towards more stuff in the future. For me though, as long as they can justify it; without retconning more stuff / seeming too ludicrous – It should be fine by my books. 