What kinds of pizza are there to make?
The classic model is the Neapolitan style, fired in a screaming hot oven with minimal toppings, e.g. the margherita with tomato, buffala mozzarella and basil. Americans seem to like to pile on a lot of crap ala California Pizza Kitchen and Pizza Hut. In Italy they would immediately start picking that stuff off and throwing it away. The crust matters.
We like to cook up a few large yellow onions in olive oil with a touch of salt until they're really soft and a bit light brown, and put those on a homemade crust with a couple big handfuls of wild rocket or arugula, some slivers of local salume, and some small bits of good mozzarella. Not authentic of course, but my non-Italian sons really love pizza made this way. pierino's suggested combination of ingredients is excellent, however, and he's absolutely right that the crust must be superb, and that the screaming hot -- love that expression -- oven is the only to achieve that. ;o)
How many flavor combinations can you imagine?
'Purists' will sneer at pizza toppings the same way primordial ooze would show distain for multi-celled organisms: "That's not how it used to be!" But without evolution of our food, we'd still be stripping down game with our teeth bared.
Which I guess means that "pink slime" would work as a pizza topping. :-) Recently I went to dinner with some friends at a pizzeria in Ojai that was reasonably good, maybe not the best ever but reasonably good. Mine was topped with arugula and speck. But one of the friends, who is English, for some reason hated it because it wasn't piled high with crap toppings like extra cheese, sausage, olives etc. There's Papa John's for that ma'am. And Chicago style deep dish pizza isn't a pizza it's a casserole.
I am definitely in the minimalist school. The varieties are indeed infinite. Just think about the size of the things you put on it. The cooking time will often be short (especially in rocking hot, neapolitan style ovens), so you don't want gobs of stuff that will burn before it heats through.
It's all about controlling the heat penetration! Thick base = lower temp = more time for the pile to get cooked. Cracker crust means fast cook no time for toppings to get much done.....