Pick a marshmallow in the backdrop and put a face on it... the write your username on the side of your marshmallow...
My drawing looks better in full screen. I went to the original project and clicked on the first remix, and then clicked on that project's first remix, and then clicked on THAT project's first remix...etc and then I arrived at the one by @slayyyy9 and remixed it, adding a drawing that I made by tracing my profile pic in Inkscape (which exports drawings as vector images, so scratch can import it without making the quality horrendous) Also, I had to export it as an optimized regular svg file, otherwise it crashes the costume editor!