Peter Quince is one of the "rude mechanicals" in A Midsummer Night's Dream, one of the craftspeople who seek to put on an impressive, tragic play for Theseus' marriage to Hippolyta. Quince is the author of the play and many scholars see him as a comic representation of Shakespeare himself; both wrote and were happy to take parts in their own plays, and both had backgrounds as craftsmen. Because of this, I think it would be fun to give a nod to Shakespeare in costuming Quince, perhaps by giving him similar facial hair to Shakespeare's famous portrait, or his receding hairline. You could even have him carry around a quill to write with and scribble furiously throughout the scenes he's in.
Looking at Quince's costume in a broader sense, his overall look depends on the setting of the play. If you stage it traditionally, in ancient Greece, Quince would likely wear a short robe in a bright color, with a rope to tie it at the waist and simple sandals. The play is so famous, though, that it could be staged in any time or place. In a modern-day production, Quince might wear a flannel shirt and overalls and sit in a Hollywood director-style chair. The key, I think, is to make sure that his costume portrays his modest origins (he is a working guy, after all), while still suggesting his plans for glory through the arts.