A couple people asked me how I created the picture for my current Facebook profile, which looks something like this:
I did it with the GIMP, and it was actually really easy. There's a few steps to follow:
1) Open up your picture in the GIMP (this is an easy step)
2) Go to Filters -> Edge-Detect -> Sobel - I use this one because it generates a lot less noise than the other ones, and it is mostly black and white. The issue is that some features which should be brighter aren't, like lips. You can experiment with some of the other Edge-Detect filters they have in there if you like.
3) Go to Colours -> Threshold. Drag the little arrow around in the histogram (which will appear on a dialog called "Threshold") until you get something you like. At this point as I mentioned in the last step certain features might not stand out, so you might have to do some tinkering with a white pencil to get those features to stand out a bit more (unfortunately I'm not an amazing artist, so the lips in that picture above look kinda wonky).
4) Remove noise. You can do this with the pencil tool to draw black over the noise, or you can use the select tool(s) to select and delete stuff (make sure to set your background colour to black). Do this until you have removed the stuff you don't want.
And tada! You should have an image that looks something like the one above.