I found an article at Dreamstime that analyzes the top 10 best selling photos at Dreamstime during 2007. It seems like family and business type photos are the most popular. Groups of people in photos are also popular probably because it’s not that easy to get good shoots of several persons in one photo. I suggest that you read the article because it gives you some really useful information about how to create best selling photos. You can read the article here!