How about:
Decent Car park, close (as in part of
) the safe zone
half-decent drainage (my cocker, unlike my woman, doesn't like eccessive mud baths), plenty of gas, the safe zone being warm and dry, a train station within easy walking or cheap cab distance (I want my car back
), maybe somewhere to sleep (tents in summer, inside a cow in winter).
Plenty of marshals, loads of (free) water in the summer, somewhere for marshals to shelter between games (preferably netted).
Not just sup'air, things like hyperball, or bale/barrel* fields (*those blue barrels which seem to be part of every paintball site ever).
Different format maybe (like the diablo 3-man a while back, 3 teams per field)
Extra trophies, such as move of the day, marshal of the day, and of course prat, of the tourney.
An easy to find site, or if it's a bit out of the way, then a few signs up from the major route.
Oh, and if you could get the moon from up there, onto a stick? That would be just champion!