You can use photos from the internet to illustrate your entries, but make sure you tell us the source - don't pass it off as yours. We check pictures at random and cheating could result in your disqualification from the entire contest.
You only have to submit each entry once! All submissions are approved manually, so it will take a while before you see yours published. Don't worry if it's not up on the website right away, it will be added a.s.a.p.!