I really like the art and ingenuity of Skeleton Key's 2E Adventure Tiles Labyrinth Core Set. You get a whopping 73 small square tiles. There are two main types of exit - and a mixture of curved walls with straights. The light grey browns will give you a maze reminiscent of dusty classical settings or from the films like Labyrinth or Barbarella, whilst still fitting within grey castle environments.
As with many geomorphic designs, some referees may not like the fact that players can see beyond the walls to an inaccessible part of a tile, but I'm sure that a creative DM can find an explanation to allow for this meta-game awareness - perhaps just a sense that there's a hollow chamber or corridor beyond the wall - all the party need to do is go around the next corner to get there... - which is pretty much what mazes are about. Certainly, the visual impact and compressed nature of the tiles mean that a maze will feel less laborourious than elongated zig zagging corridors. It might be a bit of a struggle to run 4E D&D encounters in such small areas, but many other FRP rules should be okay.
Good looking, professional and inventive.
[5 of 5 Stars!]