In general, tennis clothes are boring. Nadal is at least TRYING to suggest something new. I hate the sleeveless shirts. I pretty much think they look good on nobody. Maybe a good sleeveless design is in the future, though.
I really think making cooler tennis clothes the norm would help tremendously. If kids want to wear the clothes, even if they're not a player, it would be good publicity. A lot of tennis clothes look like golf clothes with shorts, and that's not a good thing.