Using AGM M7 with a Dark Background

My previous post mentions how I got myself an AGM M7. A simplistic phone deserves a neat background. However due to some bug in the firmware, it unfortunately does not seem possible use the phone after to setting the background to fully black. Attempting to do so will result in the user interface switching to white text on white background. Please let me know if you understand how avoid that.

The picture above is the darkest one I have managed to set with maintained readability of the android interface. It's simply a QVGA picture with all pixels set to grey. Feel free to download and use it.