[cbk1994]

24 or 32-bit images won't show up in the level editor. This means any PNG with semi-transparency or more than 256 colors, or that was exported wrong. GIFs and MNGs can always show, from what I understand, but GIFs do not support semi-transparency or more than 256 colors, which is why PNG is a superior format.

If you need to see an image offline only, you can drag it on "gif2mng.exe" in the Graal directory (C:/Graal or so), and it will make a copy as an 8-bit PNG (it converts GIFs to PNG8, PNGs that aren't 8-bit to PNG8, and animated GIFs to animated MNGs).