tile laying in need of a theme

... chocolate production?

Ah, now I understand what you're asking. You have a game like "Cacao", which is a game that already exists, but hopefully not TOO MUCH like it, and you want a different theme.

Um, coffee production?

ecosytem building. like city building but less industrial, so swamp, desert, forest, ocean etc etc.
alchemy? if you dont have to match like for like all the time this could work.
or you could keep it abstract. pretty symbols and colours.

Your theme could about making and selling alcoholic beverages. You would be Salesmen and/or workers in a Vineyard and/or Brewery and/or distillery. Alcohol is something that you can make and some time has to pass before it is worth anything, the longer you keep the more they are worth. You can also try to lay tiles that advertising and/or connoisseurs to try to boost demand and therefor price of your product. You could also have some thing like a store or private reserve to hold the proper container before selling it.

Feel free to disregard, use or improve upon. Good luck with your game.

Riffing off this - a gothic necropolis

You could have planets and planetary improvements (tiles) which people (resources) live on. Instead of selling resources player would collect money for transporting the people to newly discovered planets. The types of people could be farmers, builders, military, and scientist. Each of these could also provide some type of bonus/detriment to the planet. I am thinking that somehow the planets just produce more people every so often. As the planets become more overcrowded people are willing to pay higher prices to leave. Maybe you could also have something like alien warlords and the closer they get to the planet the more people want to leave. Also instead of playing a tile you could also use it to move your transport ship kind of like moving your explores in Karuba (https://boardgamegeek.com/boardgame/183251/karuba).

I suppose a similar them could also work for colonizing a planet or the some badlands earth.

Feel free to disregard, use or improve upon. Good luck with your game.

Good old mining, with the twist being how well the gems perform after being cut. That would be the push your luck element. You go for volume or quality when you place tiles (dig the mine).