I did some pretty massive and stunning lootbags on barbarian camps on Svarground several years ago with a LOT of items. It took me years to sell all of it, lol, maybe there I "confirmed" that the sky is the limit for parcels. But yeah, I imagine somehow if my parcel can be refused on a mailbox or something due to an outrageous amount of items. Most likely not, but not impossible to conceive some sort of limit.