I know there are several sites that sell shirts/onsies like these I loved the designs and didn't want to pay the $30+ for a onsie so what is a girl to do but break out the felt and heat n' bond and get creative
I have been one busy bee working on a ton of projects lately. There is just so much inspiration out there especially now that I have joined Pinterest . LOVE that website, it lets you make boards of ideas and pull ideas from other peoples boards too and is a place to save ideas/tutorials etc from various websites.
Here are some felt onsies I made. They aren't hard except that they are time consuming to make because you have to draw all of the designs or trace them from pictures on the web that you have enlarged etc. I used heat n' bond to "glue" the pieces onto the shirts/onsies and then you can sew around the pieces if you wish.