I just saved your second pic and opened it in GIMP. You have 2 layers right? One called Background and one called Frame 2 it says. I think you drew the GM icon on the background layer itself. That layer can't go transparent. Make a new layer, draw on that, and delete the default background layer. Since yours isn't animated you can just save a gif without doing all of that option changing stuff I mentioned earlier.
To do this easier rather than starting over, open your picture, NT, and click on the GM icon in the window that shows the layers. Click duplicate. Delete the original, not the duplicate, and then start erasing the white of the duplicate. Try that out. I hope this helps.
