I think the biggest thing you're going to have to do is hunt down 360 models and renders or research designs based on the source content you want to use. Depending which game you're looking to go for with the back then that's how you're going to have to design and study. It's something you have to do for any design. I mostly do a lot of original artwork and outfit design but I may have to do this for my OC Spartan armour when the time comes though I'll likely cheat and just do a repaint of the mark IV(?) armour with some minor mods aesthetically to match my character and her persona.