Actually you can upload any file to summitpost which does not exceed the size limit (8M sounds right). I added a java archive that way, which I sometimes use to create rotating panoramas like this.
However, only picture formats are displayed and some formats don't convert well into the avatar, thumb, small, medium and large sizes. I have had trouble with some icons (gifs) that way. The original size always works.
Thanks for the correction. The gifs I make in Photoshop only play in the original size, but the ones I make in Premiere play in all sizes...weird.
This can be done (with more steps) with free programs. I use Paint.net: