I LOVE it! Having water lines right there will make water changes easy-breezy! What do you plan on for filtration? I would, personally, do all sponge filters and run a central air system. Because you are so good at building things the central air pump could be run outside with a covering and enclosure to help reduce noise in the room itself. Just make sure to keep the pump off the ground for rainwater purposes.
This will really come out fantastic I think. The tiles on the walls are something I haven't ever seen and I really like them.
Is the metal in the ground for drainage?