Google is a good place to start for images

Usually, you can always find a large size picture that is good enough quality to use.
What I think would help to add some depth to your sig, would be to skew/distort your binary background to make it look like a long wall or somthing. I would also suggest blurring it the farther away it is, or giving it a kind of glow or something towards the front. I made this for an example, but you could go ahead and use it if you wanted to