You need to decompile the SystemUI.apk (which is the statusbar)
you can use apktool to decompile (afterall ther are plenty guides on XDA to modify statusbar)
once u've done decompiling, replace the images that you want
but dont modify .9.png i.e "9" images else apk will get corrupt or unstable.
then sign the apk and replace your modified systemUI.apk with the one in system/app
and bingo! you have a custom statusbar.