Board Thread:Support Requests - Getting Started/@comment-24319470-20140423151832/@comment-8865495-20140424022929

Well, you can always use an online editor like Pixlr to save a file into a different file format, however, you must upload a file with the specified file format on the preview image, so if the previous image was a .jpg, you cannot upload a .png over it as well as vice versa. (Anything after the however part is just about uploading images.)