You can use Add Image to put any other image from the site into your image, and then drag the corners so it fills the whole thing. If you choose one that's roughly the same dimensions, it comes out alright.
Plus, if you think outside the box, you can do a lot with the standard templates! If you look back through Invicta103's older submissions, you'll see he used to use the same 5 or 6 templates over and over for just about all his memes and comment replies - somehow he made it work.
Hope you don't mind the tip!