Well, it's not that they're lettered that's a problem, it's that you must provide direct links to the artwork, not to an index page (you're probably going to get more comments, etc. if you can post images instead of pdf files). There are a couple of other requirements, too, but you can check those out in the forum guidelines at the top of the Storytelling Lab.
So, sorry to have to do it, but this thread has to go over to the Bulletin Board. We'd love to see your work, though, so when you can give us some direct links to the work, please repost them.