Image format for Roll20 is .png, .gif, or .jpg. .png and .gif will allow transparency , and .png will be the best quality wise for transparency. Image wiki: <a href="https://wiki.roll20.net/Image_Best_Practices_for_R" rel="nofollow">https://wiki.roll20.net/Image_Best_Practices_for_R</a>... As far as software, GIMP if you aren't willing to shell out cash or photoshop if you are are probably the two biggest options (from my perspective as a non-artist, so take it for what it is worth). As far as making them look good at a wide variety of zooms/token scales, that is all dependent on their resolution (note pixel resolution, not the print DPI resolution). Ninja'd by Aaron. Good to know about the support status for .gif though.