Thanks Caenwyr! Argh seems that I'm on heavy fire to make a tutorial or giving tips
Alright here we go for the mountains : Those are hand-drawn with a graphic tablet (but in this style there's not that much tablet function used - just a very small controle pressure that's it, so that can be easily done by hand then scanned). Here's a quick one.
First draw a simple outline (here I used a small grungy round brush - no need to be too neat and clean for the style, that is intended to emulate some old 17th century style cartography mountains):
Attachment 57601
Then add "shadows" by simple curved hatching and a few dots:
Attachment 57603
Then add a bit of noise:
Attachment 57604
Once scaled down and put on a background with a dark brownish color you're done
Attachment 57605
Oh wait, now you just need to draw dozens more mountains
You can draw them all on the map or if you want to re-use them on some other projects, turn them into brushes. Here I use them as brushes. Basically I draw the mountains, keep a few individual ones and build up some ranges (horizontal, vertical, diagonal ones, in short/medium/long sizes) and build up the final ranges on the map with them.
Hope that helps