I tried this on GMFS but the folks there weren't too cooperative. I got the idea from camaro5 but the moderators just crapped on the thread by merging a "miscellaneous LOL pictures" thread into it, totally breaking the flow.
Maybe it can work here.
Here's how it works: Post a picture that's somehow related to the preceding post. If it's not obvious, explain it. So, if I post this:
then you might post this:
See, it's a trunk, like the elephant trunk above. Then the next post might be:
...because the person looking into that trunk is wearing a towel on (his? her?) head.