Thanks guys.
To answer some of the questions:
Lukc: As various people say later in the thread - I'm using TreeThing for the forests. I'm using the Vaniya Mixed brushset that I included with the program and the jungle brushes I also included - although I had to edit them somewhat as I believe some shades were missing or something. For the shadows I'm also using TreeThing, which places shadows beneath each tree but I'm also using several other layers, one of which is the template I use to generate the forest in TreeThing, all of which are filled in with a custom pattern that I made that is supposed to resemble some rough line shading.
Tostan: It's larger than that. A0 I think which is... umm.. 33" x 46"? Something like that. My PC has 2gb of ram so I guess it could take another 1gb before it reaches its cap as I'm running 32bit XP. The plan is to first get a new HDD so I can then get 64bit Windows 7 without losing anything I currently have installed, which would then allow me to utilise more ram. Well, something like that.
Schwarzkreuz: as the other guys say, I'm using a program. I'm not sure if the last version I uploaded does it or not, but when I generate a forest it gives me a count of the amount of trees in it. As all my forests span across 10 PSD's I was pretty lax with the adding and was rounding figures off. So 68k is approximate - give or take a thousand.
And yeah, I'll also be adding places and labels.
Jax - Yeah, I made the jungle using TreeThing, although to get the look I had to do quite a bit of post-imaging work in Photoshop on the generated layers. The program gives you four layers - shadows, trees, shades and masks - but the forests here have around a dozen layers and an extra four layers for the shadows. I also had to use a parameter in the program that has not been fully integrated yet or explained which is "Maximum Brush Width" I believe. Altering this fools the program into believing the actual brush images it reads are different to what they are and so the spacing of a forest is changed. So lowering this parameter will make the trees closer together - something I had to do a lot for the jungle.