When I hosted my swap a few people sent some extras, which was super nice (and of course not expected!). Some people sent fat quarters, a little extra fabric, some extra blocks specially made for me, ornaments, candy .... all of it was much appreciated!!
When I am in a swap (and not the hoestess), I too try to send something extra, being a hostess myself in the past, I know it is A LOT of work to not only get the blocks swapped out, but to package everything up, then take it to the PO and weigh everything and make sure it all has the right postage, and give change back etc .... I think they do deserve a little something extra for that, though of course the hostess would never ask for such a thing themselves. :)
Cheers!
Rachel