As a test, I attempted to upload four signature pictures to my signature. The first, which was sized properly, had no problem. The second, with dimensions too large, failed. The third with file size too large failed. The fourth, back to my original picture, had no problem.
Well my current pic, unchanged, uploaded via woodalls but not RV. I can screen cap if you like. It errors out saying the pic has to be 500x100. I even resized to 99 high in case someone put the limit at 100 and the software thought anything less than 100 was fine.
This forum software really leaves a lot to be desired.