Cargo My Eggo

I am creating portraits for most of the Twins' top prospects (Sano, Meyer, Buxton, Kepler, Salcedo, Arcia, Hicks, etc.). My problem is I can't get the portraits to upload via MVPEdit. It "says not a valid bitmap". I used Gimp and exported the main image as 24 bit and alpha as a grayscale 8 bit. 256x256. I never had a problem before, but now I can't figure out the problem.