A print swap would be fun.
Generally speaking, the rules of a print swap are up to the originator to define. Whether the prints are B&W or color, wet lab or inkjet, what sizes are acceptable, etc etc are all part of the swap's rules and definition.
I only print inkjet (since about 1994) so a wet lab print exchange I can't participate in. I do both B&W and color work, and would suggest prints that can fit into a US Letter sized document mailer as a max size, and 4x5 inch as a min size. The swap rules should also define the dates when to register for the swap, when the mailing list will be available, and when all the prints should be mailed.
Swaps are fun but require a commitment. Love doing them and seeing what everyone else is working on.