Our group used to have a Cats database and we eventually got rid of it.
That's what you get for having(had) a cat db, you have to try several times to delete it before it actually does.
But seriously, were there originally any images or similar external file uploaded in any of those db fields? If yes, that could explain it, the db deletion process cleaned everything but not the "embedded" (linked) images, probably stored at the same place uploaded wiki images go to, and this is a bug after all. (I presume one can have (embedded/linked) images in the db fields, I admit I haven't looked at the Database functionality a lot as we are not using it in our groups)
