Decorate your tub however you like, ribbons, photos, stickers. If you're a scrap-booker...then treat it like a page (just remember if you plan on putting an acetate cover to protect it, it needs to be flat.
When satisfied with your decorations wrap the tub with the acetate and attach the end with some "clear" tape where they meet. I also run some along the top and bottom to seal and finish.
I kept one of these in the back of my car so if out and about and the pooch needed to go, I just pulled out a couple of baggies and was ready when he was.