This is an excellent point, and one I've thought about from time to time. If you are giving the players an in-game handout, especially in a fantasy campaign, it is probably not going to be a photo-realistic representation of the terrain. Of course, in a high-tech world, or in a very high-magic world, more accurate and photo-representational maps become possible. Maybe even ubiquitous. But where's the fun in that?
I've never done this for a real game, but one option that I've played with a little is flattening my map and importing it into a new document
- I then took my tablet and VERY loosely traced over it, purposefully leaving out some details, altering others, and exaggerating a few more.
- Hand draw some icons...
- Use Photoshop/Painter/Gimp and experiment with getting a watercolor or ink-wash feel
- Of course the background has to be parchment. Or a well-preserved leaf. Or a piece of bark. Or a carved stone. Or anything else that important information might have been writ upon. Or scrawled quickly upon. Or drawn surreptitiously upon.
It's great to look at "Olde" style maps for reference here. Some mapmakers would represent more important features in a larger scale... Surprise!
Of course, while their scale might not be constant, they could provide a "standardizing" mechansim, much like the distance written on the Gough map that you linked to.
All in all, I think it's a great idea, and helps to not only set the tone of the world, but also immerse players in it, as their characters scratch their heads over a map and say "but shouldn't the village of HoldFall be right /here/?"
An untested method off the top of my head (VERY quick & dirty):
-Take your original map
-Create an outline from it, or from specific layers within it - I would have to play a little here... Find Edges? Anyone?
-Distort slightly (in PS w/ liquify)
-Replace some features with Icons, Image Hoses, Stamps or Pattern fills
-Add some Adjustment Layers to pull the color scheme together (Sepia? Inda Ink? Multiple colors of Ink/Watercolor washes? Your choice)
-Throw a quick texture over the whole thing to simulate parchment, fabric, or whatever your map is drawn on.
I may give it a try later, when I have some time to boot up PS and fiddle...