I made my bag out of felt and sewed in pleats on the sides using one long rectangular piece, and instead of straps I threaded some black cording through the folded seam.
As far as the design, I used a borrowed image that I printed on the non-shiny side of freezer paper, cut it out to make a stencil and used silver paint to fill it in.
I may make another one for the twilight swap that I'm hosting. I love this!!!!