If you have a stack of these blank cards, you could do a lot of things: play library, dream about the books you will check out at the library, think of a list of names that might be on the card (or what book title…?)
Or you might glue cut-out phrases/words to them that you will later use in writing poetry. And when you’ve done that, you might paint them.
That’s what I did in June, 2020. Take a look at this array.