I'm big on DIY, less expensive solutions, but unglazed quarry tiles are a bit of a gamble. Because they aren't made for the thermal shock of baking bread/pizza, there is a small possibility they can chip. If one of these chips/shards get's into your bread/pizza crust and you or a guest bites into it, it will chip your tooth. Believe me, I know.
It's better to use materials specifically engineered for the shock of baking - a baking stone or fire brick. I went with fire brick because it was a LOT cheaper and the thermal mass was gargantuan.
Swinchen, one thing to be aware of with fire brick is that it is HEAVY. I was able to find 12 x 12 x 2 fire tiles that I cut to fit my oven. The oven shelf was a bit iffy with the weight, though. I ended up going to a ceramic supplier and buying kiln supports to prop up the bottom shelf.
Remember too, that you'll want 1" clearance on all sides for proper air flow.
If you really want to go crazy reproducing pizzeria style pizza at home, get quarry tiles to create a ceiling on the shelf about 10" above your hearth. That's all you need. A nice thick fire brick hearth, a thick tile ceiling and about an hour preheat at 600. Combine that with a mozzerella/parm, sauce, high protein, lean dough - pulled thin and you've got quintessential NY style pizza.