I have used a gradated roll-up backdrop in grey for photographing my 3-D artwork.I bought it on Ebay for under $20.It has since faded to a blue tone that I dislike,so I now use a large piece of grey formica,purchased at Home Depot,that I curve and adjust the lights to get the same gradation in the background.

For shooting product shots here at work I just use a large sheet of recycled cardboard that I curl up against the wall and for other portrait work I use solid colored bed sheets. It works.