Duly noted. We'll definitely consider this for a future release of SEUM. I'd still love to hear from others who might also be interested in this feature. Feel free to chime in!
This should be fairly easy to do from a programming standpoint. Download the image, calculate a checksum. Subsequent fetches are compared against that checksum. I've done that many times before using wget and md5sum, obviously on Linux boxes.
In practice you could implement something similar using a smoke page and leveraging the existing player. Ultimately it would be best to have the SEUM Player integrate that functionality but it would be one alternative that could be implemented immediately.
You can consider this my vote to add image validation as a feature request. This is something I'm sure our customers would like to have.
Solarwinds added the ability to "match image" in the latest release of SEUM. Thanks guys!