New to the Guild and looking for tips!

[kde.rockstar]

Howdy gang!
I'm starting in on my first attempt at mapping with GIMP and really exploring the software. I studied architecture in school and used Photoshop for many years there. Now that I'm out of school (and their computer labs) and trying to avoid software piracy I'm exploring the open source world and really enjoying what I'm finding. I tried some initial mapping in Inkscape but found that the intricacy I was working at just better suited to a raster image so I moved over.
I'm starting a brand new Pathfinder game in a few weeks and I'm working on some initial maps to set up the campaign world. Here's first large area where I expect the lion's share of the campaign to take place. It's a large inland lake (roughly the same area as Lake Superior) which has several medium size sovereign nations around it. Overall waterflow goes from the large river coming out of the NE and flows out to sea in the SW.

map2.jpg

I used two modified brush sets from fellow Guild member Wag, found here. Many thanks to Wag on that as I'd initially made my own and they looked horrid. They worked great as standalone elements, but I knew I'd need a little more density to my map elements and added internal opacity to the fill area of the trees and mountains so that I could use them to draw the dense, overlapping areas you see in my map.
Although doing a bit of color airbrushing under the mountains has worked okay for me, I'm not sure the same tactic will work as well under the trees or across what I'm trying to express as grassy plains. I haven't added any hills yet, but they are planned around most of the mountain ranges as transitional elements.
Anyone have good tutorials or examples for border/page elements? Although I'm printing this out on actual paper eventually, I want to give it more of an aged parchment look with some good fades, stains, and tears at the edges. Maybe even some fold lines. I've seen great examples of these (especially folds - you guys are really impressive!) but haven't found tutorials I can replicate the effects of yet.