I did it because I didn't find it as a standalone anywhere else. It's no new thing but I thought of sharing this just in case others might find it useful.
So big thanks to C3C076 for sharing the source code of his application and hopefully some of you will enjoy this.
I've attached the apk, the source code and a screenshot.
Xposed Full Screen Call Picture should work on any device having Xposed 2.1 or greater and Android 4.1 or greater (google based rom.. as mentioned in the GravityBox post "pure or close to pure Android").
Not working with:
- Sense (reported by anant210)
- Touchwiz (reported by oldslowdiver)
Now the module can be downloaded from the Xposed Repository.