So... this is a bit late. International Self Portrait Day is always on November 1st, and I did manage to squeeze in a little time to take part this year (and then plain forgot to post here!).
I'm still working on my personal sketch limitations - 4 colours maximum, solid blocks and hard edges only (techniques like hatching not allowed), and seeing how far I can go with it. I'd have liked to have had more time, but it was at a premium that day so I had to make do, and got it done with just minutes to spare! Anyway, it's a great idea to get involved in challenges like this, or Drawllowe'en, or Inktober (which I'm now committing to for 2017) as you can really stretch yourself if you like, you can experiment with styles you wouldn't normally use but with some structure to the challenge (which some people, myself included, like as a change of pace from personal work which is entirely unguided), and you're taking part in something with other people across the world - that's an awesome feeling.
Thanks for looking!