If the caption comp was popular, maybe it could be continued in a slightly different way - a picture as before, and then write a limerick rather than a caption.
I think the numbers dropped off because a reminder wasn't posted on the general board - just the winners name. Maybe if there was a pinned note that the caption comp could be found on the competitions board might be helpful?

Another idea - as photo comps have been popular in the past, perhaps a photo representing one of Joanna's CDs might be an idea? As there are loads of CDs, both new and old to choose from (I can just see a messy rabbit Christmas photo!!), it might work for a year at least -but pin a reminder on the discussion board.

Just a couple of thoughts. Janet