Picture Order

What determines the order in which pictures appear in your gallery?  Can the order be changed?

For example, I'd like progressive weight-loss pictures to be shown in order of loss, but they seem to upload to whichever location they want, and I can't figure out how to re-arrange them.

Thanks!

Crickets seem to chirp whenever this question is asked. I would also love to see an answer to it ... anyone out there have suggestions/tips?