bantin on "image in front of page"

I'm looking for a way to add an image to the front of my website.

I have an image that's like a picture frame with a transparent center. I'd like a way to put it on top of my site such that the site contents (text blocks, images, videos, etc.) scroll behind it. It would be kind of like looking at the site through a window.

The frame would be fixed like a background image, but the content of the page would scroll behind it.

Any ideas?

Thanks