Dynamically create interpolated hollows and bumps in terrain

Hi, I want to create a static soccer game like this table soccer

Since I want to be able to have different board setups, and perhaps even allow players to create custom setups, I'd like to generate a hollow wherever there is a soccer player. But I also have to make sure the terrain is never flat, otherwise the ball could come to a stop, so I need bumps between each players, but It has to be smooth bumps (as per the picture)

Is there a way to do this through script? Actually, i don't even have any idea how to do this in photoshop if I wanted to do heightmaps instead of through code.