Cooked and crumbled sausage of your choice; smoked sausage, minced; grilled filet, finely chopped; sautéed or grilled mushrooms, finely chopped; cooked and crumbled ground turkey, chicken or beef; duck confit, minced.
For cheese, I prefer either stronger, sharper cheeses alone, or those mixed with a milder soft cheese. One can take a hard, sharper cheese (e.g., Parmigiano, extra-sharp cheddar, aged goat, among others) and grate it finely, mixing it with another cheese (milder or not), or mixing it with a soft spreadable cheese like soft goat, cream or mascarpone.
Herbs are a nice inclusion and other things work well too. Try minced toasted almonds with, say, crumbled cooked sausage mixed with grated Manchego and mascarpone, with a little fresh thyme. For a twist, to that add some minced reconstituted dry cherries.
Lots of possibilities.