In order for you to claim compensation from the paintball operator, negligence or liability of some kind has to be proven against him . If you trip over a tree root and break a leg then the company are not liable, as i undersatnd it, because a tree root is a naturally occurring piece of woodland 'furniture' and any sensible adult would be aware that there are natural trip hazards in the woods. If however you stand on a nail sticking out of a plank of wood that used to be attached to a barricade that the paintball operator put there then this IS his responsibility so he could be proven liable for your injury.
Even with naturally occurring hazards there is some liability - eg a tree has become unsafe and is leaning at a 45 degree angle but the operator has ignored this even though you can prove that someone brought it to the operators attention on a previous visit to the site a few weeks ago. If he knew about it he should have taken action to remove the risk - either closed that field or felled the tree. If however all seemed well with the tree (ie it was standing up straight) but a strong wind brought it down suddenly then he has not been negligent as he didn't know the risk was there. (Although there could be some argument that in severe weather such as a gale or a storm he should have known that woodlands can be unsafe places and should have halted the day). He should have a record of inspection for each field. We cant assume a field is safe because it was last week / yesterday. I 'm pretty sure operators have a duty to make and record regular inspections of their fields and identify any new risks that may occur. We (Delta Force) have a generic risk assessment (company wide for things like guns, co2, compressed air, pyros etc) and a location specific risk assessment (as each centre is a bit different) for every centre. Field/carpark/basecamp inspections are documented once a week with diagrams of risks and this is fed into the maintenance team and a visual is carried out each morning for anything new since the last game day.
It also helps if someone else has been sucessful in claiming compensation in the past as there is said to be 'precedence' in Law. You might check that out?
Don't know if any of that can be applied to your circumstances or not....