The ability to have the Portal Window use an Image

[FrankingtonGanties]

Much like how the header can use an image as a background, it would be cool to be able to do the same thing to the portal window as well. I'd personally use it to try and get the texture of parchment or cloth. It would even better if I could some how get the uneven outline you would expect from a piece of parchment or cloth.