I prefer 1024x1024 with no compression. I've made bigger maps but I get more freezing and crashing in poser with larger sizes and I have a good system as these things go. If you don't compress at all 1024x1024 looks really good. The difference between the image quality lost through .jpg compression vs. size reduction is no contest to me.

"Your work is to keep cranking the flywheel that turns the gears that spin the belt in the engine of belief that keeps you and your desk in midair."

Annie Dillard