It has a forum with several topics. Most of them asking for penpals (only, no postcards). And there are other types of “postcrossings”: toys, little journals, etc. ;)

Oh! Arriving to the postcrossing site and reading its frontpage, I thought it was just for postcards. Didn’t know about that! Thank you very much for the tip! Will definitely look into it. Sounds fun, especially the “other types of postcrossing”! :D