A conversion step will not turn a picture of three animals plus a mop into an adoption card. Those files go back to the volunteer with a specific request: one animal, one subject, a little air around the ears.
The clinic's front-desk computer runs Windows. The volunteers who photograph the animals use iPhones. For two weeks in a row, the adoption-board JPGs we thought we had received were actually HEIC files, and the waiting-room PC opened them as blank tiles. We stopped emailing "can you export that again?" and started converting the files in the browser, on the same machine that prints the cards, without sending the photos out of the building. The originals stay in an "as sent" folder. Converted files are named with the kennel ID. We proof the print on the actual cork board, not only on the monitor. Photos that are really a hallway, a shoe, or three animals at once go back to the photographer instead of being forced onto the board.