[baronchar]

(being only in my early 20s but suspecting that I am one of the older people around here), I don't think you can be too old to cosplay; there are plenty of older characters in anime and as long as you're still into it, you shouldn't hold back.

personally, I've been Orochimaru and Kiba from Naruto (on separate occassions, obvoiusly), Kurosaki Ichigo from Bleach, and Inuyasha from Inuyasha.

and to concur with the previous comment, it's best to make your own costumes and I find that to be a great part of the fun!