EDIT: It looks like I got this wrong, as the cards will cost $1 with this code.
Walgreen's is giving away free custom photo 5×7 Mother's Day cards thru 5/15/17! Using code 1OTGXOBQBKHZF at checkout, you can get the card completely free with in-store pickup. It's crazy how similar the free code looks to what my dog typed when she jumped on my lap just now.
While this is a Mother's Day promo, you should be able to use this code for any custom photo card, not just Mother's Day cards.