Guardian Eyewitness is such a great app on iPad, and I wish it had a feature allowing you to set the images as a wallpaper for that day. Being able to rotate wallpapers would be even better. Unfortunately, it won't let us do that, at least not in the current version.
However, if you have a jailbroken iPad, it should be easy to do this. First, you need to know the location of the wallpaper, which is
Then, you need to find out the location where Eyewitness app stores the Photos. For my ipad, it is
I don't know how the cryptic names like 7C322A28-737A-48DC-8535-08878D6001ED are derived, and I found it out using trial and error, but I believe tools like iFile have a setting in their plist that allow you to see both the encoded name and the actual app name.
For now, I just overwrote HomeBackground.jpg with one of the photos in this app, and respringed. It should be possible to write a script that runs once in a while in background, and automatically rotates between available pictures. Let's see when I have a relatively free weekend to try this out - back to work for now.