This is a very subjective. Everyone has their own built in set of criteria which can even change on a day to day basis, depending on their mood.

I can tell you what turns me off though, is a thumbnail which does not represent the actual image.

I think in the end all you can do is create an image which evokes a response in you. If other people don't like it, oh well. Keep on rendering!

I don't think you can look for any cookbook solution here; there really isn't any. What i will generally do is try and step outside myself and ask would I click on this thumbnail if I was someone else.

I do agree with other posters and I have seen this myself that once an artist reaches a certain status, people will click and drool on those images simply because they are from that artist. I aspire to reach that point someday! I just heard Vicki say "in your dreams!" :-)

Given the number of people who visit these websites, you will probably always find a group of people who like your images or your style. And I believe that is the major point; every person has a slightly different style. And maybe this is what really draws people to click on certain images.

Hope this if helpful.