Spray help?

I’ve been attempting to make a transparent spray for Gmod in GIMP for about a week now. I make sure it’s the right size (256x256) and the right file type (.tga) but once i import it it shows this:

http://filesmelt.com/dl/fucking_wow.jpg

try making it a bmp or something by converting it. Steams spray things can get quite confusing and files get corrupted for wierd reasons.