Here’s a few ones I came up with that would be fun:
1: Concert Festival of Love: This would probably fit best as a summer event. It’d be based on the 60’s summer of love, and would feature music as a theme for the costumes. The first set I thought of would be a Beatles tribute with Raynor (John Lennon), Anduin (Paul McCartney), ETC (George Harrison), and Chen (Ringo Starr). Raynor’s gun and Anduin’s sword would be shaped like guitars, ETC would carry a sitar for his guitar, and Chen would carry a giant drumstick for his staff and his keg would look like a giant drum. The special would be a yellow submarine, or something close to that if they parody it a bit.
A second pack would be Malfurion and Tyrande as hippies, with more “groovy” and “chilled” lines. (They fit perfectly with the hippie free love and nature thing)
2: Butchie and Murkie. This would be a toon-styled costume pack, featuring the Butcher and Murky as a “Tom and Jerry” type cartoon. Their costumes would make them “squash and stretch” with exaggerated features you’d see in an old cartoon with anvils and dynamite and all sorts. The premise would be Butchie is out to eat Murkie, and Murkie continues to evade him and outsmart him, leaving Butchie often flattened and blown up.
3: Sailor Elune and the Titan Scouts: This is a fun anime-based one I thought of. It would feature Tyrande and several other characters in a parody theme of the classic magic girl anime. Tyrande, in a magic girl outfit, would be Sailor Elune, and a few other girls would be the other scouts. These could include: Sailor Norgannon (Jaina Proudmoore or Mei as Sailor Mercury), Sailor Golganeth (Cassia as Sailor Jupiter), Sailor Khazgoroth (Li-Ming as Sailor Mars), and Sailor Amanthul (Whitemane as Sailor Venus). In additional, Malfurion would be Tuxedo Mal and Sylvannas would be Queen Slyl (A parody of Queen Beryl) The theme mount would be big cats (as in just big house cats, not actual tigers or lions).
4: Diablowatch: A crossover event I thought combining Overwatch and Diablo. Here, Overwatch is a fantasy-themed organization that watches over Hell, and the agents are now Nephelaem. Overwatch characters would be merged with the classic Diablo classes, while retaining their abilities in a new theme. For example, Lucio would now be a witch doctor, who controls magical drums that play his music, while Zarya would be a paladin whose shields are magical light based.