Lots of choices for sure. What part of the world are you in? Do you have shady spots on the proposed deck, or will it be all sun-exposed?
I ask because, for example, using Pennsylvania Bluestone as decking in southern climes is pretty brutally hot on toes and buns! In my world your choices go from brick pavers, travertine, concrete pavers, brushed concrete, "cool deck", spraydeck, and combos of stone and grass/gravel. You want to match or compliment your pool coping and tile (or vinyl liner color/pattern), too.