Try experimenting with a variety of cheeses. Just about any meltable cheese will work. Some recipes call for all cheddar cheese, others use varieties like asiago, romano and gorgonzola.
You can use any small pasta shape that has holes for holding sauce, like ziti, pinwheels, or elbow macaroni.
You can also add cooked vegetables to your macaroni and cheese: mushrooms, broccoli florets, and peas are all possibilities.
To make your own bread crumbs (much tastier than the kind you get in a can), cut the crusts off a slice or two of white bread and process in the food processor until fine. Voilà.