What resolution, size, do you normally post pictures for this thread?
A couple of months ago I ran into a problem when trying to post large jpegs directly to the server and it turned out that there were a couple of constraints on image size. The first was the file size which appears to be limited to files smaller than either 1.1 or 1.3 MBs, not sure which one. The other limit is pixel dimension. The Macrumors support team wasn't able to give me an exact number but for a 1 MB file it looked like a 4800 x 3200 pixel image was acceptable. Their recommendation was to bring the resolution down to 1620 x 1080 and work with the jpeg quality to bring it under a 1 MB limit.