Encouraged by OlduvaiGeorge, I’ve been experimenting again with my Wacom tablet, in Photoshop. This is my latest creation, based on a fast ballpoint-sketch:

To show you that it’s not difficult at all, I wrote this “making of”, explaining the basis process and techniques used for the textures on the cloths.
Read on:

2. Open your drawing in Photoshop and place a new layer above the sketch.
Grab the brush tool and select a hard brush, size between 5 and 9.
Now start tracing your lines with the stylus.

If you’re done, delete the layer with the pen drawing.

3. For the textures on the clothes and the color of the skin, I used pictures from SXC.hu.
Throw in the picture you’d like to use, in a layer under the line-art. Adjust the size with the free transform tool (ctrl+T) and place it on the right spot.

Then add a layer mask to the photo layer and fill everything with black, so it’s not visible anymore. Now you can let it reappear by brushing with white over the areas where you want the texture.

For example, this is how I made the jeans:

And the pull and the skin:

Notice I don’t always stay “within the lines”, if another color layer is coming above it (like the hair or the shirt).

For the hair I started by brushing with a brown color under the line-art layer and then adding a picture of (blond) hair, wich I then set to blending mode multiply.
(Afterwars I merged this two hair-layers by first linking them through clicking in the box next to the eye-icon in the layers palette so an anchor shows up, and then layer>merge linked.)

Take a look at my layer order:

4. To achieve a shading effect, paint with a soft brush on new layer in a darker shade of your texture color, in the case of the jeans I used a dark blue. Then set the blending mode of this layer to “darken” and the opacity at 67%.

5. As a finishing touch, I added a picture of an old sheet of paper , wich I placed underneath all the other layers.

Here’s the finished result: