Ahhh, another classic case of staring at something too long. In config-int I had given the correct $pp_db_prefix value, but I'd given it in the commented out example line, rather than the uncommented actual variable definition. *sigh* I can't wait for the day when there's a switch for finding the obvious error you just _know_ you're missing in something.
Now that I've made a few edits to inc_features to display the thumbs as I want, it's all working just fine. Quick quesiton though. The featured photo box is set to display the latest photos, but is not displaying the ones in member galleries. Is this a correction of the previously present issue of non-members being able to see member gallery photos? Or do I have something weird going on?