The background you choose to photograph your work on may depend on your specific type of work.
Neutral backgrounds such as gray, beige or black or the ever popular graduated photo paper often work best. These are widely available at photographic supply stores and are well worth the investment. Just note, they are delicate and need to be taken care of- wrinkles, scuffs and scratches can be unsightly in photographs.
Smooth fabric can also be used. But, if you use fabric, be wary of wrinkles and fold marks, they can be very distracting.
Some jewelers use translucent glass lit from beneath for that magazine ready look.
Some artists even choose to shoot their images in situ or in interesting venues such as their backyard. This can be done to great effect, but be careful that the background enhances rather than detracts from your work. And, some show juries can be rather conservative, so unless you know that they will not be put off by such images, it may be better to use a plainer backdrop for jury shots. The same goes for props- just make sure they play a supporting role rather than stealing the scene.