Fiona, have you thought about Chicken Saltimbocca? It's not that dissimilar to what you're already making.
Chicken Fajitas
Chicken-Fried Chicken Breast with Mashed spuds and Cream Gravy (Sounds redundant, but is REALLY good)
My other half likes me to make a basic Duxelles stuffing, stuff the chicken with that, sear, place in a casserole, saute onions, garlic, mushrooms, and seasonings in the same pan the chicken was cooked in, deglaze with a touch of white wine, add some cream of mushroom, stir until smooth, and bake for an hour.
Make a cornbread/andouille stuffing, stuff the chicken, sear and bake (we do this at work, with skin-on double breasts rolled around the stuffing).
Make a crab stuffing, maybe with a bit of good cheese, sear and bake.
I've made a cheesy, Tex-Mex chicken/rice casserole that's really good (although I use dark meat).
Maybe some kind of stuffing with Italian sausage? The fat from the sausage will help keep the breasts moist.
Rubbed with a Mexican-style rub, grilled, with a mango/pineapple salsa.
Sauteed, add shallots and apricots, deglaze with white wine or brandy.
Broiled with Mango butter.
Normandy Chicken - sauteed, add shallots and cooking apples, deglaze with apple brandy, add some cream, simmer to marry the flavors.
Bread the chicken, pan-fry or bake in the oven, top with bacon and cheese, and return to the oven to melt the cheese.
Traverse City Chicken - saute, add shallots, reconstituted dried cherries, deglaze with Kirsch, add cream, simmer to marry flavors and complete the cooking.
Make a Mole Sauce, saute the chicken, and top with a little of the Mole, serve with Mexican rice.
I could go on and go.