Paintball2 supports the regular Quake2 deathmatch entities and keys.  These are the ones that are new or have been modified: 
 

worldspawn

gamemode

maxteams

team#

sky

weapon_pballgun

item_pballhopper

item_pballammo

item_pballco2

item_pballbarrel

info_player_deathmatch

(under construction)

• Format: "classname" "worldspawn"
• Description: The worldspawn entity defines the properties of the "world" or entire level.  You can set things such as the default gravity, sky, team colors, etc.  This is the entity where all the brushes are.  It is basically the level itself.

• Format: "gamemode" "#"
• Values for #:
• 0     All game modes
• 1     Deathmatch
• 2     Single flag
• 4     2 or more flag mode (flag in base)
• 8     Siege
• 16    KOTH (king of the hill)
• 32768 Debug only
• Description: Add these values together if you want an entity to be in one or more game modes.  This can be applied to ANY entity, but must be applied to the worldspawn in order for the map to be able to run with the modes.
• Example: "gamemode" "18" will make the entity appear in KOTH and Single flag modes.  If applied to the worldspawn, the map will only run in KOTH and Single flag modes.

• Format: "maxteams" "#"
• Values for #: Any integer from 2 to 4.
• Description: This is a key in the worldspawn that indicates the number of teams that can play on the map.  You can have 2 to 4 teams.
• Example: "maxteams" "2" will make it so only 2 teams can play on the map (like for regular 2-flag CTF).

• Format: "team#" "color"
• Values for #: Any integer from 1 to 4.
• Values for color: "red" "blue" "yellow" "purple"
• Description: This is a key in the worldspawn that indicates what team is what.  It is used to determine what color an entity, player, or base will be when the teamnumber key is used.  You can use any combination of the 4 colors (just not more than one team with the same color).
• Example:
"team1" "red" 
"team2" "blue" 
• That will make the first team red and second team blue, like regular 'ol CTF colors.

• Format: "sky" "sky_name rotate_speed rotate_x rotate_y rotate_z"
• Values for "sky_name":
• "unit1_"     Id's red-orange sky.
• "pbsky1"     Cloudy sky - resembles Quake1
• "pbsky2"     Sky with the sun
• "pbsky3"     Starry sky
• Description: This is a worldspawn key that will set what sky to use in a map.  The sky names listed above are currently the only ones that can be used.  If one of the Quake2 skies is used, it will look messed up due to the fact that the palette is totally different.
• Example: "sky" "pbsky3" will make the map have a sky like the one in "Midnight Paint."

• Format: "classname" "weapon_pballgun"
• Keys: 
• "type" "gun_type"
• "group" "###"
• Values for "gun_type":
• "low"     (spawns trracer or stingray)
• "medium"  (spawns vm68, carbine, or spyder)
• "high"    (spawns autococker or automag)
• "trracer"
• "stingray"
• "vm68"
• "carbine"
• "spyder"
• "autococker"
• "automag"
• Description: This places a paintball gun in your level.  The "type" will give you a specific type of paintball gun.  If you don't give it a type, it will spawn a random weapon when the map is loaded.
• Example:
"classname" "weapon_pballgun" 
"type" "medium" 
• That will randomly spawn a medium power paintball gun, such as a vm-68, 68 carbine, or spyder.

• Format: "classname" "item_pballhopper"
• Keys:
• "type" "hopper_type"
• "group" "###"
• Values for "hopper_type"
• "100"
• "200"
• "300"
• Description: This places a hopper in your level.  The "type" will let you specify the size of hopper you want (how many balls it is capable of holding).  It will be random if no type is given.
• Example:
"classname" "item_pballhopper" 
"type" "200" 
• That will spawn a hopper that can hold 200 paintballs.

• Format: "classname" "item_pballammo"
• Keys:
• "type" "ammo_type"
• "group" "###"
• Values for "ammo_type"
• "small"     (25, 50, or 100)
• "medium"    (50, 100, or 150)
• "large"     (100, 150, or 200)
• "25"
• "50"
• "100"
• "150"
• "200"
• Description: This places an ammo box in your level.  The "type" will let you specify the number of balls in the ammo box.  It will be random if no type is given.
• Example:
"classname" "item_pballammo" 
"type" "medium" 
That will spawn an ammo box with 50, 100, or 150 paintballs (random each spawn).

• Format: "classname" "item_pballco2"
• Keys: 
• "type" "co2_type"
• "group" "###"
• Values for "co2_type":
• "small"     (12g or 7oz)
• "medium"    (7oz or 12oz)
• "large"     (12oz or 20oz)
• "12g"
• "7oz"
• "12oz"
• "20oz"
• Description: This places a CO2 canister in your level.  The "type" will give you a specific size of CO2 canister.  If you don't give it a type, it will spawn a random size every time it spawns/respawns.
• Example:
"classname" "item_pballco2" 
"type" "medium" 
• That will randomly spawn a medium sized CO2 canister.  It will be a 7oz or 12oz when it appears.

• Format: "classname" "item_pballbarrel"
• Keys: 
• "type" "barrel_type"
• "group" "###"
• Values for "barrel_type":
• "brass"
• "chrome"
• "steel"
• Description: This places a barrel in your level.  The "type" will give you a specific type of barrel.  If you don't give it a type, it will spawn a random type of barrel.  Brass is the worst barrel, steel is the best.
• Example:
"classname" "item_pballbarrel" 
"type" "steel" 
• That will spawn a steel barrel.  A steel barrel gives a player the greatest distance and accuracy.