It would be awesome, but with Dave so overwhelmed with requests right now, I've come up with my own temporary fix before bothering him with more. In several of the forums over in Clematis, I put a sticky at the top of the forum with an index. I alphabetized the entries in each index with a link to that particular thread. So, if you want to see if a cultivar has been posted, just click on the index and look it up. If it's there, you can click on the link and add your own photo. If it's not in the index, then you can start a new thread and add it, just like we could add things to PlantFiles if they weren't already there.
EDIT: Though there are thousands of clematis cultivars, there are a limited number currently available here in North America. So, it's feasible to set up a separate image gallery of those that actually are available here. I get so frustrated when I see a photo of a "must have" clematis only to find out it's not commercially available here.