Help with background on a design

[TammyBell]

I have a copy of a design that has several villians inside of the Mirror frame and on top says "Just Visiting with a Few of my Friends". I would like to put this on a peacock blue t-shirt, but would like to have a background color and possibly a frame/border around it so that I can print it on dark transfer paper. Could anyone help me with this? I have the image if you need a copy.