Got it, I'd previously done everything you mentioned, what got me was that I needed to set the preview screen to "not hidden" and, my most sreious problem was that I needed to save and close the editor, also, I wasn't sure when you ment war3mapPreview.tga as in just "war3mapPreview.tga" or "war3mapPreview/(Image).tga" kinda stupid I guess, but I ultimately figured out it was the former, literally just as you said.