Felix, I would suggest that either you limit the event to paintings that are ones Bob did or slight variations like same painting without a cabin. I have sent hundreds of students to your site as the best place to search and discover various paintings by Bob.
My experience with other sites like Facebook groups around Bob is that artists who are not following Bob’s technique at all get accepted and post odd paintings that have nothing to do with Bob. There are plenty of art sites - I would urge you to keep this focused on Bob and his work.
At a minimum, every event should have a category of “Best execution of a Bob Painting”.