Another fat you can use is "Caul Fat". This is the fatty connective tissue that helps to hold the intestines in place. It looks like a lace doilie. Supposedly gives a nice crisp texture on the exterior as well as keeps the meat in the middle moist.
There's another technique, called "Larding", where you take julienne strips of fatback, clamp them into special needle, and stick the needle through the meat, pulling it out the other side, and clipping the fat off so the fat remains inside the meat. It's a good substitute for marbling. Don't ask me where to get "Larding Needles". I've only seen them once, in college, and never in my professional career have I heard of it since.