I don't know what exactly you mean by scenario, since you only have about 20 people I wouldn't make them to elaborate. But here are a couple simple scenarios to get you started:
Downed Pilot
Downed Pilot is a game where one person either volunteers or is selected in some way to be the Downed Pilot, while all the other players become Hunters. To give the Downed Pilot some kind of an advantage, he gets a semi-automatic marker and something to use as a shield or the Downed Pilot gets to carry as much paint as he wants, while the Hunters are restricted to only twenty paintballs per person. The object of the game is simple, if you’re the Downed Pilot: Survive! If you are the Hunter: Eliminate the Downed Pilot. Note: If your group is rather large, you may wish to have two Downed Pilots in the game.
Rules
· If the Downed Pilot has the semi-automatic/shield option, hits on the shield do not count as an elimination.
· The Downed Pilot has a five-minute head start into the playing area and a signal must be given so the Downed Pilot knows when the game has started.
· All Hunters must start at the same time and place.
· When using the limited paint option, if a Hunter runs out of paint he is out of the game.
· Players who are eliminated may not communicate in any way to either team, such as indicating any intentions or locations of opposing team members.
· Players who are hit are eliminated from the game.
The Drop
The Drop is a game that preferably requires two equal teams, where one team has a Courier that must carry either a gear bag or a brief case to a designated location (also known as the Drop). The Courier cannot bring a paintball marker into the game and must rely on his teammates for protection. The opposing team is known as the Interceptors, who must try and stop the Drop from occurring. For the Courier team to win all Interceptors must be eliminated or they must successfully make the Drop. For the Interceptors to win they must eliminate the Courier and stop the drop from occurring.
Rules
· The bag or case cannot leave the Courier for any reason, he must be holding it at all times. If the Courier is eliminated the game is over.
· Players who are hit are eliminated from the game.
· Both teams must start at their designated locations and cannot leave that area until the game begins.
· Players who are eliminated may not communicate in any way to either team, such as indicating any intentions or locations of opposing team members.