Why not letting everybody choose their favorite theme within a list of... why not 3 themes ?
I used to administrate a phpBB forum and I could enable something like "let user choose the visual theme". I just had to upload some themes so they can choose which one they prefer !
And if some just wanna cry about what it looks, let's cry babies :p
[EDIT] Okay I missed some lines just before my message, the idea has already been said. Sorry