I do not know how to create maps or if Terminal Overload already permits this, but I have made some rough sketches and ideas for some maps. You find them as an PDF attachment.
Some notes about the symbols:
Black lines denote cell borders. Everything outside is considered “the rest of the map”; normally, it should normally not be easy or even possible to reach.
The starting zones are marked with the team’s numbers. All other cells are considered neutral.
To denote hills, I use a blue “arrow”. The arrow points uphill. If not noted otherwise, all cells are flat.
Areas which have been crossed-out in red are not a cell to be taken. They are intended to be obstacles as well.
Red lines or dots are obstacles.
Notes about special maps:
Bowl: This is a circle which is becomes slightly lower towards the center.
King of the Hill (both variants): The 4 crossed-out squares should go uphill to. The whole point of this map is that there is a hill in the center of the map, located in the 9 center cells. The center cell shall be flat again.
King of the Hill (4 teams): This sketch is intended for a 4 team play, in case Terminal Overload will ever be able to support 4 teams.
Spirals: The blue area should be higher than the cells. It should be something like a somewhat steep climb, like in ETH1.
Walls: The 4 large crossed-out areas should be really large obstacles, the 8 small ones should be somehow walls, not that tall but still tall enough to be not able to look above it.
The other maps should be self-explanationary.