Hey, I'm new to this community.
I made a tutorial for this icon:



I don't know if it's of any use to anybody, but I just thought I'd post it anyway...
I made it with PS 6, but I'm pretty sure, with proper knowledge, it can be translated to any other program, if not... Sorry. And it's my first tutorial, so it's probably not very clear. But feel free to ask if there's something you don't understand, and I'll try my best to explain...



First, get the picture you want to use, rezise and crop it if necessary. I'm using this one:



Make a new layer and select the pen tool. Always make a new layer for each new part of the picture. On my picture, I started just at the edge of Matt's neck, and then start adding anchor points. The easiest thing is to just go across the parts that will cover the face, like the hair.



Once you've done that, connect to the first Anchor point to make a solid shape. Then hold down the mousebutton over the pen-tool button. A drop-down menu will appear. Choose "Add Anchor Point" (the one with a plus sign).
Now, you can start adjusting your path. Just click anywhere on the path, and a new anchor point will be added. By pulling this, you can bend the path. Like so:



It's quite hard to see, because the picture doesn't have a lot of "bendy" edges. But, as you can see, I didn't adjust the line that goes across the hair. That's because the hair is going to cover that part anyway.
When you've done that, it's time for coloring!
Choose the eyedropper tool, and choose a good color. I simply clicked on his face, and adjusted the color to my liking slightly. After this, right-click and choose Fill Path. Make it's set to forground and then click OK.
Your image should look something like this now:



Now, that just looks like a big block of color, right?
Hide that layer, and make another one. Repeat the previous step on the different parts, just make sure that every block of color is on a separate layer.
Do the larger parts with the pen tool, like eyes, mouth, eyebrows, nostrils etc. The smaller lines, like shadows, are easier to do with a small brush.

(If you want, you can make a stroke around the outline of it, but it isn't necessary)

I'm sorry if this is hard to understand, english isn't my first language, and I'm not very good at explaining...
Anyway, if you HAVE managed to follow my strange instructions, you should have something that resembles this by now.



If you don't, feel free to ask me questions or yell at me.

Now, you can either delete the layer with the original picture on it, and make a different background to it. If you want to do what I did, then make a new layer, fill it with white and drag it to the bottom, so that it's underneath all the other layers. Then select the layer with the original picture on it. Go to Filter > Artistic > Cutout and choose the following properties:
Number of Levels: 4
Edge Simplicity: 4
Edge Fidelity: 2

Fiddle around with the opacity of that layer until you get the result you want. I left mine at 56.
Then just add a brush, and maybe some text if you'd like, and that's it!

Sorry if it's hard to understand... Feel free to ask me any questions if something isn't clear, which it probably isn't...


Before


After