Write captions for the Tate. The Tate is asking for submissions for captions for its artworks if you think you can do better. This is nicely open in as much as the staff admit that there could easily be punter sout there with more expertise than then on particular artists. It however does not seem to be soliciting facetious or misleading tags, which is a bit of a pity.
I actually think much of the labelling in the Tate is pretty good. It is a difficult subject after all. You do not want to lead the viewer into making connectiosn they would not necessarily make from the work. It is an adjunct, unless the name is part of the art (which of course it often is). But at least they have labels unlike some places: say the Memling Museum in Bruges.