I mocked up a super simple thing like this in HTML5/JS here
It is the simplest it could possibly be just every pixel an even chance of being foreground or background and mirrored.
There's a wierd bug in Firefox where every sprite is identical (RNG seems to be getting reset or not reseeding, if I stick an alert in between tiles they do generate nicely, wierd.
), but it works fine in Chrome (apart from the ubiquitous blur).
Refresh to regenerate. If you've got chrome hit the image button to get an image to save.