I have changed the Needs Updating Tag so that:
1) it applies to more than just images (cause as far as I can tell, we needed this, I couldn't find other relevant tags and this one had a pretty usable name)
2) it's huge and obvious so users can know that the article is out of date and not rely heavily on information within (as well as encourage editors to make the changes so the ugly thing can go away)
3) has various useful links encouraging good editing habits and fixes.
Scratch that, I've decided to overhaul parts of the wiki in a "Things to Do" project. Go here for details.