My client is running a program that customers sign up for and become certified after taking a course. After becoming certified, they get a "certified" graphic that goes in the customers email signature. This test has to be taken multiple times a year.
My issue: If the customer fails the test, we have no way to revoke the certified image. Is there an email service that can serve out a non-downloadable image/object that can change based on our customers status?
You are going to run into a significant problem finding such software. Here is why: As soon as the end user sees the image on their computer they have already downloaded it. The image has to be sent to their computer so that they can see it. There are various tricks you can try to attempt to make it harder to download such as using javascript to disable right clicking it, using multiple images overlaid with obfuscated CSS, or using an unusual format that they hopefully won't know what to do with when they get the image, but all of these are simply ways to forestall the inevitable. A computer savvy user knows that because the image is on his screen it has already been downloaded and he can get at it one way or another. For instance he can take a screen shot of it and crop it.
Another thing that might serve your purpose is to watermark the date issued or expiration date into the image. If done correctly this could be quite hard to remove and at least people would know it is old. If you do this, make your image larger with lots of detail that would be hard to recreate.
