black is great, but make sure you spary it with some of the anti-static stuff - it attracts fuzzies like mad! lolol
Also, by now some stores have inexpensive costume fabrics on sale. Crushed velvet in a dark color looks really rich, too
In an ivory or dark burgundy/black/purple it would make your bows stand out really nice.
Oh, and most of the crushed velvets are knit, not woven, so they are really easy to stretch over the canvas without wrinkles (which wouldn't show anyways because of the fabric's texture LOLOL)