Yay! Someone's still interested in my work! Thanks, Fugitivo!
The Hourglass Pyramid is also probably still one of my favourites, despite it being much simpler than the original concept. I had first imagined it to be a giant (and functional) hourglass in the desert, constructed with pyramidesque blocks. I would've gone for TerraEsperZ's idea of two pyramids with one stacked on top of the other upside-down giving an overall hourglass-like shape but that didn't work out either, as I had trouble with the perspective on the top half. I had to settle for a "carved-in-the-cliff-wall" thing when time was (literally) running out.
That choice hopefully didn't take away too much of what the concept for the inside is. I imagined it to be an hourglass that actually flipped upside down, also with puzzles dependent on the sand level. If it was in 3D, imagine Ocarina Of Time's Water Temple (with sand instead of water) combined with the last main dungeon in Majora's Mask (the name of it escapes me now, you know, the one that flips upside-down). But in 2D, you often wouldn't see the ceilings above you (the floor when flipped). I was overly ambitious with five floors from top to bottom (but when flipped, gave up to ten), which was simplified to three - though now you never see the top "floor", and not much happens in the center room, so it's really more like two main ones. As you probably guessed, the darker-coloured floors are what you see at night, and the brighter-coloured ones are what you see during the day. As with all dungeons I filled in the rooms as I went, but I always kept in mind that you would have to come to this dungeon in both day and night to complete it (kind of like the Spirit Temple in Ocarina Of Time being visited twice). As it is, it's the only dungeon in this game that uses the day/night idea - all the other dungeons can only be visited either during the day or at night but not both.
The sandy areas you see in the center of each floor would've flowed outward as if it were a pile of sand being poured onto at the center (just like inside an hourglass, of course).
At least I still managed to fully pull off something I always wanted to see...Zelda dungeon floors being as round as possible. I did that by using the circle tool, and then covering the circle I created with the appropriate tiles. I think they look pretty cool on that alone.
Oh yeah, to answer your other question...I've also gotten two requests to use some concepts from this for fan games. To anyone else wondering, I'd be fine with that, though if you directly use any of the (few) original tiles, or any particular concepts, it would be nice to mention VGMaps.com, even if it's just a "Special Thanks" in the credits. That's just common sense courtesy.