As long as you don't dress up like this clown for a tennis match, you're fine::twisted:
(No offense to Fed, but his Wimbledon outfits are sometimes a bit too much for my taste...
)
To give a more serious answer:
Wearing bandanas etc for practical purposes is fine. I don't think there is a certain NTRP required for being allowed to use certain parts of equipment.
However, the emphasis is on pracitcal purposes, wear stuff that you actually need. I.e. don't get a bag with room for 12 rackets if you've only been playing for half a year and don't wear bandanas just to look good.
And like some other guys said: It's hard to draw a line here but it shouldn't look like you're trying to be your favorite pro player. It will always seem funny to some people and it's an even bigger joke if you don't have the game to back it up.