Here's a question for you: I don't think this challenge traditionally included cover pictures, and I can't remember if I've included them from time to time, but I'm happy to make this change. I changed this month's post to include them. What do you think about a more general change to allow them?
I think it might depend on the actual Challenge theme. For some topics adding pix might be too broad. For others it would be perfect, and could be stated in the theme's rules. But that's just my opinion.
As an example in the Never Judge a Book By Its Cover Challenge, Secretariat sometimes allows words in the title, sometimes it has to do with the author's name, sometimes a picture, and sometimes a combination of any of the above that she chooses.
[For example, in the Ultimate Challenge 's July's theme of verbs. There may be no verb in the title, but for any book with a person, or even an animal, I could make up an explanation that a character on the cover was doing something that fit for almost every cover. Like sitting, sleeping, dreaming, thinking. In my opinion, it would be too broad. But that's just me. You're the boss here!]