It's a easy process... Any one can do this!!!
At first take Contacts. apk of a ROM which you want to mod.. Then decompile it with apktool or NinjaMorph.
You will find some folders......
Open "res" folder the search for folder "drawable-nodpi" open it you will find some PNG images...
Search for the PNG file "background_dial_holo_dark.PNG" .. replace it with any PNG with the same name "background_dial_holo_dark.PNG"!!!
After done recompile the apk and push in to system>app by root explorer and reboot your phone.......
And enjoy the new dialer background……
N.B- I cannot make sure that it will work, but I have done it in my MTK phone and it worked..
HIT A THANKS IF I HAVE HELPED YOU