John it depends on what you can do or make. do you make props, figures, or mostly 2d. Like shawn said, the idea is to flood the market and offer as many options as possible. I make prop sets, meaning they are complete kits or sets. I include backgrounds and many aditional props within the set for a low price. I've been told I need to charge more but I'm not in it for the money. I just like the creativity drive and fix I get from completeing a new project. the money is just a perk for me. this is my sight at renderosity.

http://market.renderosity.com/mod/bcs/index.php?vendor=359238

adding 2d backgrounds to your market in 1200 x 1200 pix will generate a little more income. use your digital camera and take pictures of nature, city streets, old buildings ect. and don't forget closeups for textures like brick, stone, plantlife and so on. all these can be marketable for you at renderosity