Playing paintball in the woods is particularly interesting because players create the combat field, making bunkers and other needed features. Here is a little help for you if you decide to create woods filed, according to your needs.
You must supply few things. You will need old tires, shipping pallets, flags that will be used for marking, netting or privacy fence, pencil and paper.
Bring your friends and play one game in the woods before you create the battlefield. That way you will be able to see which the places that need improvement or added cover are. Give the players small flags and tell them to mark the places. Maybe this can be done only by walking through the woods but it's more precise if it's done while playing.
Construct an overhead view of the field. Place the bunkers on the marked locations, having in mind the natural features of the woods, for example large trees or gullies. Think well because the main idea of this is to add necessary elements to realize the competitive and the strategic side of the game, but the final field should look as natural as possible.
Make the bunkers and place them on the mark places. Use natural materials as large rocks, stones, fallen trees and leafs to create bunkers where needed. It is better to find them first and then to place them in the paintball field. Maybe you are not going to be able to find enough material so in that case dig a pit and build mound using old tires. After that, cover the tires with dirt. Bunker can be build from used shipping pallets as well. In this situation, cover the face of the bunker with fallen limbs and brush to camouflage it. Thing is to look like it fits with the landscape.
Not to disturb anyone with the shooter games, build a privacy fence or hang a net along the side that is within shooting distance of another person's property.