These are really fun. The other day I was at an antique store that had a rack filled with old Mad and Cracked magazines.
I was just in awe at the superb way that the illustrators were able to come up with such great parody visuals. It really seems like the best comic imagery is something that is both almost instantly recognizable while also being a bit surreal.
This is one of the reasons that I like L.H.O.O.Q http://en.wikipedia.org/wiki/L.H.O.O.Q. so much, putting a mustache on (arguably) the most famous painting of all time, changed the entire context.
The Onion is really doing a great job, both in writing and images, I hope they can continue for a long time.