I've been making calzone (and sometimes just bread, though it's a bit sweet) using this recipe for some time now. Yesterday, I actually used it for pizza, of all things. The best part about pizza (or calzone) is that you can use random toppings/fillings and they'll taste pretty good.
Staples for pizza are baby spinach, mushrooms, and perhaps onions, but there's plenty more to try. Black beans are a bit unusual, but quite good on pizza, it turns out. Today I'm trying adding some ricotta cheese (part with mozarella, part as the only cheese--if you don't hate ricotta cheese, TRY THIS). Green bell peppers, of course, are always an option. Tomato works. (Yes, I know there's already tomato sauce.) Extra garlic on top is a good idea.
Perhaps the best pizza I ever had included artichoke hearts. Sadly, I don't have those.
What should I try next? Sprouts? Corns and peas? Curry powder? Chili powder? Cottage cheese? Potato? (Oooh, potato! Probably a bit flavourless, though.)
Pineapple does not belong on pizza. Nor do carrots. Sweet = bad unless it's a pizzert.