Over on Mastodon - though obviously anyone anywhere can participate - there's a weekly monster-film watching event called #Monsterdon where we all watch a movie together and comment as it's running.
One of the regulars made a bingo card for last Sunday's movie, and being a Godzilla movie, I of course had to make 3D-printable TOHO stamps to go with it.
I used 20% wood-infill PHA, since it's got that little bit of softness that helps with things like stamps, and 20% wood infill variant to help take up ink.
Even with an FDM printer and a 0.6mm nozzle I was able to get a very usable/functional result! The positive is only 20mm across (and the negative/invert only a couple of millimetres more) and yet detail is reasonably preserved.
First layer is extremely important, though I guess that goes without saying. But I think you can make some decent - not amazing, not as good as real rubber stamp material, but decent - stamps this way if you wanted.
image of stamps and bingo card
