OK, so I've received some complements on my mountains in my recent maps so I decided to make a quick tutorial on how I draw them...
While simple upside-down 'v' mountains or rendered terrain mountains and forest textures are excellent ways to show physical features on a map, very cool looking mountains, forests, and other elements can be created by hand with very little effort (provided that you have access to a scanner).
The first part takes place on paper (preferably card stock or something harder than printer paper) and is detailed with examples in the first attachment. Although this is specifically for mountains, the general techniques can be used for making trees, hills, dunes, snowdrifts, canyons, mesas, etc.:
1. Draw a simple outline of a peak (I use a 0.1-0.35 mm sketching marker (technically, a 'pigment liner') for this step).
2. Draw a line down approximately the middle of your mountain from the peak to the base - jagged for a tall, sharp mountain (like the Himalayas) or smoothish for an older, eroded mountain range.
3. Add heavy shading to the inside of one side of your mountain... this is the side that will be shaded from the sun and should be the same on ALL FEATURES on the same map. I always shade the right side but it's up to you... do not shade a solid line on the base of the mountain, only along the ridge you drew in step 2 and one side of the outline. Other rock formations can be added into the dark side of the mountain right now by shading them in solid (see step three picture... the line in the middle of the dark side would be an example of a rock formation)
4. Draw horizontal lines from one shaded line to the other across the dark side of the mountain. If it looks too light (judge by your eye), cross hatch the shading near the top or just scribble around a bit inside until it looks right. You don't have to use this method for shading - you could fill the dark side in solid or come up with your own method after experimenting with different things.
5. Shade the outline of the lighted side, adding indentations or ridges wherever you want (try not to add too many or it will look too cluttered and not realistic). Shade these in as you see fit, solid.
6. Add very small horizontal lines perpendicular to the general form of all ridges and rock formations on the mountain. See example picture from step 6 on the first attachment, it's difficult to explain exactly what I do here. Again, you can come up with your own technique for this or disregard this step entirely.
7. (combined with 6 in attachment) Draw some random horizontal lines at the base, scattering them to represent the base of the mountain. Keep in mind the ridges you drew and how far out they would jut from the general shape of the base of the mountain.
And there you have it. Also shown in the attachment are steps for drawing trees, hills, and sand dunes/snowdrifts.
Now all you have to do is scan your drawings into the computer (It's good to have 6+ different mountains for your map... more if you make different types of mountains... for example, if all of your mountains were pretty much cone shaped with similar ridges separating the light and dark side, you could probably get away with 5-7 different mountains without much notice). Once you have them in, open the document in photoshop and scale it however you want... keep the original file so that you can create brushes at different scales (adjusting the radius on the brush tool in PS itself causes blurring of the mountains, which will look weird alongside sharper symbols that were not adjusted) for continental, regional, and city maps (unless of course you want to draw more detailed mountains the smaller scale you go... )
Select each mountain with the lasso tool and create a brush for it using the Edit > Define Brush Preset command.
With this you can craft mountain ranges by carefully placing mountain brushes on your map (see the 'composite range example' in the third attachment). Alternatively, you could draw the entire range by hand and scan that in (see 'drawn range example' in second attachment). Both styles look nice in my opinion so use the one you like best or, again, try to come up with your own.
And that's it for now... after I work on my technique myself I might post a tutorial about how to draw terrain, such as grasslands, marshes, etc.
I've attached some examples of completed trees and mountains that you can feel free to use in your maps if you want. Happy drawing =)