Need a place to shop for posters, wall scrolls, etc

I was wondering if anyone could recommend a good place to shop for anime artwork (posters, wall scrolls, etc).

Most of the shops/sites that I use for buying anime and figures seem to have only the popular artwork available.

I suppose I could search Ebay or Amazon...but I don't know how to check to make sure they aren't knock-off copies or whatnot. (~_~)

Any suggestions?