Proposal: Remove entries from users who are not active on this site, starting with entries from users that have been inactive the longest.
Rationale: A major problem with the photo contest is the only way to remove an entry from the list is for it to "win". With over 450 entries, it can run for 8-9 years with minimal involvement. With an expected wait time of about 4 years, there's little incentive for new participants.
Further, "winners" may not have been active on the site for years by the time their photos are featured. The current winner, for instance, was "Last seen Aug 9 '17 at 14:20".