I know you made this with a sharpie, but since it's digital now (scanned in), perhaps some colors would make areas stand out for the viewer of the map? In GIMP, I would make a new layer and change the layer mode to multiply. Then you can color on the multiplied layer and the color will blend through to your map. The example is a PNG (the board wouldn't allow me to attach the XCF nor a TIFF).Name:  Example.png
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