Depends on the kind of fractal and the software that I am using. If it's a non-flame UF image, I work small, sometimes 640x480, because I know I can render to whatever size I want and not loose a spec of detail. If it's Apo combined with Photoshop, I work as big as my rendering patients will allow. I usually can't wait around for 3 days for an iteration density of 3000 to render, so those are usually small. I'm still shocked when I hear of large Apophysis renders. Either you guys do iteration densities of 10, or you have supercomputers, or you don't mind waiting for days.