I have been looking through the image proxy logs and see lots of entries pointing to images from the old VB gallery install, which I have not deleted yet. What is odd about a lot of these entries is that there is no referrer log. Other entries pointing to third party image sites like photobucket show the referrer (ie forum posts) in the logs.
What could be the cause of these entries with no referrers? A cached copy of the thread from a search engine? People link directly to the image from anther site?