Hi,
We have a couple of sticky's to help people with posting pictures if that is any help.
Sticky one video tutorial.
Sticky two.
There may be a few chnges as we recently upgraded the site but they should give you the idea.
One possible reason for failure is too large images (both pixel size and file size) so it's worth while shrinking them down to 800 pixels wide before uploading - this also means you can fit more of them in your gallery which is never a bad thing.
dr del