I decided to start a caricature of Hugh Laurie aka Gregory House MD! I'll work on this a little every morning until I'm satisfied, which I'm not at the moment. Some elements look like they'll work okay, some I'm not happy with yet (particularly his chin/jaw area - needs to definitely be more 'House-like'!).
So I tried something with this morning's sketch. I loaded a 'medium round dots' paper texture which I got from a 'Painter X Wow!' book CD, and chalked in the grey dots to get some nice shading effects!
The cool thing is I can change the darkness/colour of the chalk I use to get different shades, whilst keeping the same size dots - makes it look a little different.