For the Halloween season, I had the kids do a parody of American Gothic, Halloweens style.
This is the one time during the year where they are allowed to be as gory or disgusting or bloody as they want - surprisingly, most kids chose to be relatively tame, which is actually nice.They could also pick a different theme if Halloween was not their thing.
We had pictures of the painting American Gothic by Grant Wood, as well as various examples of parodies I found on the net for inspiration.