Red always compliments orange nice! Not for sure what type of look you are going for, but you could possibly just mask off the flames and do the skulls in a red color within the flames, and then add a black pinstripe on the edge of the flames. If you have alot of skulls within the flames, it will give it quite a bit more of a 'red' look versus the orange. Then the black pinstripe will really bring it out.
if you can do some airbrushed drop shadows, this will really give it a nice 3D look