Hi!
It is always good to see other people doing hand drawn maps. It is definitely a good start!
Let's see, pointers...
1. That flecks of rock that is clearly on the bottom on the canyon floor IN THE SHADOW falling from the canyon side, is not suppose to be that bright. They are in the shadow.
2. If you are on something like Photoshop or gimp, I can teach you a trick with doing the shadows easier and be able to tweak them later without having to redo stuff or overlap shadows on a weird way while making changes:
I am taking your lineart layer is on top?
<->Create layer somewhere, doesn't really matter, you are going to hide this layer. Let's call it SOLID HIGH-GROUND
On "Solid High-ground" pick the base Hard round brush. Pick a vivid color, like very bright blue. Next, paint on your actual high ground. Like on top of the canyon and on the BIGGER rocks on the canyon floor. >> What will happen is you have something to Alpha to select and then invert. This means, you can actually paint shadows without hitting the TOP of the stuff. We will get to what will happen on top. HIDE this layer. (Not visible)
Shadow_Tut1.jpeg
Shadow_Tut_2.jpeg
<-> So, now create a layer just below the lineart layer and DEFINITELY above the color layer. Let's call this layer CAST SHADOWS.
On "Cast Shadows" take a soft edge round brush,(Small soft edge) --Or you can use a hard round brush but that necessitates an extra step-- With your chosen brush, pick a BLACK color, or almost black deserty brown. Though for the tut, use black. This is still on the "Cast Shadows" layer. WITHOUT changing the opacity of the BRUSH. (Don't do it!) Change the LAYER's opacity to 80 for now.
Alpha to select on the "Solid High-ground" layer. (If you understand how to do that, just ask if you don't.) INVERT that selection.
Go back to "Cast shadows layer" (This is important. Pick ONE direction from where the SUN or Moon is shining. And stick with that direction) Now with that round brush and for now black selected, paint in the shadows the canyon rocks will throw on the ground. (This layer is above the color layer remember) so the things that needs to be in shadow will be in shadow. Also, remember, this a canyon, it won't have a small cast shadow, that thing will go a ways away from the rock.
Now, having done that, put "Cast Shadows" on multiply layer mode. Then you can play with the LAYER's opacity to choose how dark your cast shadow layer is or not. Try it. Though, for cast shadows, don't go below something like 65% for layer opacity.
Shadow_Tut_3.jpeg
<-> Create a layer ABOVE "Cast Shadows" layer. Let's call it CORE SHADOWS.
Core shadows are quite a bit darker than cast shadows. But, the difference is, they are close to the edges and not nearly as big as cast shadows.
REPEAT the steps with the cast shadows layer, but keep these new shadows small and close to the edges. (Also, AFTER using Alpha to select like with the cast shadows step, to add your core shadows along the edges, go back to select NONE and on the "Core Shadows" layer, start painting on the rock faces themselves, where you think there wouldn't be much light, remember to keep it small, this layer is going to be DARK shadows.
Put, "Core Shadows" layer on multiply layer mode too. Put the layer opacity to something like 70% and resist going below that. Because it is multiplying with the previous layer, it is lower opacity layer, but it is darker on the image.
Shadow_Tut_4.jpeg
This is for having an idea what difference it makes. Normally, I take a bit more time to fine tune my shadows, but for these pictures the idea comes across.
You already some feel for highlights, but the darker shadows will make the highlights pop even more. If you like this tut, I can walk you through highlights next?
I hope this helps you some.
EDIT:
As I did the pictures, I realised I had to mention not to paint the Blue across the main lines where your ridge is. Because when I you add the cast shadows and there is place that it is over it, it creates a light patch, which is awkward to fix if not done directly.