Next are the mountains. The original map uses crescents of short strokes to show the general "downhill" shape of Jamaica's ridge of mountains, and its highest peak (Blue Mountain). With geodata, we can grab this too:
Click image for larger version. 

Name:	jamaica03..png 
Views:	930 
Size:	19.0 KB 
ID:	23109
We place overlapping crescents along the ridgeline:
Click image for larger version. 

Name:	jamaica04..png 
Views:	99 
Size:	26.5 KB 
ID:	23107
and stroke them:
Click image for larger version. 

Name:	jamaica05..png 
Views:	107 
Size:	27.4 KB 
ID:	23108
This still looks pretty mechanical, though. We can improve the look a lot by adding just a little bit of randomness; it looks like the strokes on the original map were hand-engraved, so this isn't a stretch:
Click image for larger version. 

Name:	jamaica06..png 
Views:	218 
Size:	28.3 KB 
ID:	23106