A WikiGnome is a creature who, quietly and un-obtrusively, makes many small improvements to a WikiWiki. A WikiGnome will not necessarily add content, instead adding links, correcting spelling mistakes, toning down WikiTrolls and making clarifications.
While only admins are able to delete offensive attachments, you can attach another file with the same name to replace a troubling attachment. Note that you can't attach an empty (zero byte size) file. — JMiner
See also: WikiGardener