Please do not post "print ready" images on Renderosity. It will greatly increase the download times to your viewing audience. Images for easy web-viewing are generally 72dpi and about 800-1000 pixels (or 6.773cm - 8.467cm) wide.
If an image is selected for print work, a larger version will be requested, so it might be a good to have one ready. You never know when you might get picked for print!)