I recently saw this while doing some shopping for Christmas presents. I really like the look of it, but want to replicate that into something I could wear. The last time I checked, I outgrew onesies a long time ago.
The first thing you want to do is find something worth putting onto a shirt. I found this butterfly from Graphics Fairy. Don't worry if you don't like butterflies, she has a TON of stuff you can choose from! You definitely want something simple though. Don't worry about the color or details because all you want is the outline. I copied & pasted it onto a Word document so I could size it to what I needed it to be, printed it, then cut it out of fabric.
|Recognize this? It's the same fabric I used to cover my frame!|
Place the cut out on the inside of the shirt with the wrong side up.
Sew along the edge of the cut out.
|This is what the outside of the shirt will look like after sewing.|
Snip a small hole in the shirt within the outline of the shape.
Cut all the way around the outline so the new fabric shows through.