It’s a nice topic and a fun forum idea 
One thing I don’t find so convincing is using Topic Thumbnails throughout every view. It seems ambiguous: do you want members to engage in conversations or share photos? If you want to get conversations going then the thumbnails make it more difficult to browse lists. The need for having an image also puts a higher hurdle on actually starting a new topic.
Two ideas:
- How about rather having a dedicated gallery category for images and organizing it with tags?
- on a recent theme we used the topic list thumbnails component. But we added custom css to only highlight specific topics (tagged as “featured”). This gives a more natural flow to the layout overall and doesn’t complicate having just plain topics as well:
