I make bookmarks from failed paintings or croppings by cutting them into 1- x 5-inch pieces, punching a hole in the top, and tying colorful yarn or ribbon through the hole. These pieces also can be used for gift tags.
I’ve also found that I seem to use up my stationery faster than its matching envelopes. So, I make greeting cards out of 90-lb. paper, which I fold to fit these envelopes, by painting on the paper or creating a collage for my family and friends.