Each listing is allowed 1 free photo.
The site has disk space limits and with today's cameras, people are
getting HUGE file sizes on their pictures. Pictures not less than 2Mb
file size will not be accepted and you will get some weird error
To reduce the file size of your picture reduce the image size to
e.g. 100x100 pixels. It will still look ok on the site and you'll sell
more stuff with faster loading images, so don't fret :)