DIY Bear Kiddo Tee: Cool T-shirt Crafts for Kids and Teens. This could also be adapted to create a tee using other artwork by your kids.
Im not a princess, I'm a Khaleesi - Game Of Thrones Baby Playsuit / Bodysuit
Hand Embroidered Cactus Pocket Tee by bearannything on Etsy
I'm in the Scream Team baby body vest by TwinkleJellyDesigns