OK, so it's a bit pricey but the new 'Desert of Athas' Dungeon tiles from Wizards have a great DL/desert feel about them (well, most of them do...)

They also include a great 3D adobe-style (possibly- my knowledge of 19th century American architecture is wobbly at best) hut and staircase, with a nice raft/pier walkway thingy for the desert-meets-water tiles. The tiles are all marked in 1 inch squares.