there once was something similar and it produced 7 contributions and iirc I still have one of the hidden pieces on my hdd...
That's awesome. I hadn't seen that, but it's another great idea.
I think both of these would make for fun activities, but maybe only one of them should run at a time. Unless the idea is to keep the Exquisite Corpse going indefinitely, in which case we could either continue that old one or start anew at any time.
I wouldn't think the collaborative background would be fit for a Blitz, but it is similar. Not sure how that one should be organized. To solve issues of choosing the puzzle pieces, PixelJoint's collaborative project had rules like this:
"The first 5 tiles may be anywhere at all and require no neighboring tiles."
"From the 6th tile on your tile MUST have at least one neighboring tile already posted that your tile blends into."
Of course, they had 72 tiles in that image. There are also rules about palettes, scale, and light sources to keep things consistent.
I'm just posting this for reference in case it would help anyone who decides to run one of these activities. I'd love to see it, even if only as an observer, but it might be a good challenge for me as an artist as well.