Say you write me a cheque for $50 and I photoshop that into $500, how can they detect that?
I did not touch the serial number and, as the summary suggests, the photo was taken with a lousy cell-phone camera.
If they have a minimal requirement for picture quality, the system will most likely reject a lot of deposit attempts (motion-blur, out of focus, low resolution, etc..)
Doesn't really seem worth the trouble.
The goal of science is to build better mousetraps. The goal of nature is to build better mice.