What would be a good way to print these out so they're somewhat uniform? I'm not too worried about backing or whatever since I'm using the bag, but I want some kind of uniformity
I print them out on a single-sheet sticker then carefully cut them using a straight edge and a razor. I'd then stick them on some spare Carcassonne tiles. Since the back wouldn't be an issue for you, you might consider buying a copy of The Count of Carcassonne and using those tiles. Once the stickers are on the tiles you can trim any overhang off the stickers.