Since I've used pyramids for a couple of my games, I'll go ahead and answer too:
# Why did you use the Tree house pyramids to make your game?
I love the way the pyramids offer unique gaming opportunities (Taking advantage of the colors, the stacking, etc...) They're also really nice looking and fit the whole "game from outer space" theme which for a science fiction lover such as myself, it's perfect. I also like how they're perfect for mixing with other components like boards, piecepack sets, cards, etc... The possibilities are great.
# How did you get your idea?
In many of my games I got inspiration from other mediums like computer games. My better Icehouse game was directly inspired by an old computer game where you had to program computer viruses that would fight each other. If there's a concept I like somewhere else, I look for ways to make it into a board game, usually changing the original concept in the process. This means I usually design theme first, looking for ways to implement the theme into mechanics playable with the Icehouse pyramids (plus other components if necessary).
# Could you describe the process you go through to turn your idea into a finished game?
I usually first just think about different possible ideas in my head, imagining how they could be made into a game (sometimes even dreaming about the possible games). When there's something that seems to work I try using the pieces I've got around to test different ways of working with the idea. I usually use Icehouse pieces and a piecepack set, but may also use other boards (5x5 or chess), cards, etc... then once the game begins to take shape I play some solo games and then (hopefully) some games with my girlfriend. She is usually a big help in removing problems and refining the desing.