This is the handy script ZSMTurker came up with. I changed the generic 'Spoiler' designations to specify 'Image Spoiler' or 'Video Spoiler' (lets you know what kind of content is inside, and differentiates them from spoiler tags used in the original post). With v1.0c, it now supports both Xenforo (MTurkGrind) and vBulletin (MTurkForum and TurkerNation), and has improved handling of images inside links.
See also: my MTG thread post
For many more MTurk-related userscripts, see the Turking Scripts set