Here I have some models of "tile improvements" for the Terra Nova 4X game.
I attempted to go for a quite simplistic style for them.
The tile improvement models contained in this pack:
Camp - Probably for forest tiles.
Farm - Food-yielding tile improvement.
Fishery - Offshore tile improvement that provides food yield.
Fortress - Advanced fortification building that provides better defensive bonus for units on it, but also with a longer construction time.
Industrial Compound - In case of low productivity, this will help to boost your industry a bit. Removes food yield on the tile, however.
Military Base - Basic fortification tile improvement for early game.
Mine - Can improve tiles with mineral resources, provides productivity boost.
Offshore Platform - Improves offshore resource tiles and provides productivity yield.
Oil Refinery - Can improve land-based oil tiles. Yields productivity (and possibly power as well).
Plantation - Improves tiles that has plants of great economical values like spice and cotton. Yields money.
Solar Plant - Basic power yielding tile improvement (if power is ever to be implemented in the game).
Starport - Yields money.
Suburb - Increases population limit of the city it is adjacently or diagonally attached to by 5.
You can help by EXPANDING IT.