Tiny baseball card sized mix media art piece entitled "Infernal Brute"... 2.5" x 3.5" that I sold on eBay 2017 rendered on two plys of card stock using colored pencils, black ink pen and a lil' bit of acrylic paint, then sealed with varnish.
This is what's called "ACEO" (artist card editions & originals) which basically means anything you can think of to put on a baseball card sized medium (canvas, cardstock, anything goes)... it's kind of a fad and they're highly collectible.
If you haven't tried it you should, ACEO's are a lot of fun to make and you don't have to be some kind of expert artist (I'm certainly not, lol!!!)... if you have some of your own to share, let me know because I definitely want to see them!