An amazing effect can be accomplished by setting in a zipper, and then installing grommets on each side to give the effect of lacing. The usual example of this category is, of course, the vinyl shoulder strap purse. If this is unavailable, a fanny pack, backpack, or diaper bag is good. Failing that, at least wear a fringed leather pouch with your nobles, or an embossed velvet one with your peasant costume. Any modern shoe is good, however, the judges will award extra points to such masterpieces of wrong thinking as high heels or strappy sandals.
Tennis shoes are fine.
Men wearing ladies' high heeled boots are warmly received. 1950's rhinestone jewelry is de riguer, but occult-ish cast pewter pieces are also great, especially with a noble costume. Just because you're in costume is no reason not to look good. Wear your hair down, preferably in a fluffy layered cut, and be sure it's frosted, streaked, or dyed a completely unatural color. Avoid red dye, though, as it actually was popular in period.