1 - Upload the pictures on an external site
2 - Add the link to the picture in the Gallery part (don't use the File tag!)
3 - Add after this link the description in italic characters
Example temporary available on the Sony HB-10 page (Test picture at the end of the Gallery)
I have some experience with fixing broken mediawikis at work (because my colleague's always break it ) and wouldn't mind having a look if the admins are to busy...