I saw some threads here discussion about remaking a paintball game in a modern engine like CryEngine or UnrealEngine and bringing it on Steam.
Then I noticed that I already finished all that, but I used Torque3D instead, similar to CryEngine, but free and open source and it is the most advanced open source engine existing today.
The game has modern realistic graphics and physics and is easy to modify. It is not about paintball only, but has multiple games within itself and paintball is the second game inside the game now.
So in case anyone wants to check it out:
http://store.steampowered.com/app/391780/or
http://uebergame.com