Ideas for theme that makes sense?

Hi all, first posting.

I'm currently fiddling with a game where the players will buy tiles of buildings and then try to place them as a city in front of them according to certain placement rules. A carpenter for instance must be placed where a supply of people is provided and will in turn generate wood. A little bit like Carcassonne in that each tile cannot fit everywhere and that the result is a map of sorts.

Now, a friend of mine looked at my pre-alpha prototype and suggested I considered other themes than a medieval city (he was fascinated and said the game was not just geography but in fact described a process, which is what i aim for), and I actually have done that. The thing is, the game idea started with a mechanic I wanted to try out, and I thought about what type of game that particular mechanic would fit, and came to the conclusion of a tile placement game. So, this game springs completely from the mechanics and I needed a theme to wrap it in (feels very german, I'm quite pleased with that... ;).

The reason I continued with this theme is that it is familiar, when people see a building they have no problem guessing where it will fit in the game. A farm is a basic production building that probably brings food, a monument is a prestige building that grant victory points. I thought of a SF-theme, but found it hard to relate to the tech tree.

My question is simple, can you suggest other themes where the player would more or less naturally have a feel for what to acomplish. Right now the buildings produce 5-7 different resources, but that doesn't have to be goods, it could be different mana, skills, political influence or whatever.

Any input is greatly appreciated!

/ Anders from Sweden

admin edit: moved to New game ideas forum. -seo