I found an interesting YouTube video of someone creating messenger-style people icons
Final image from the video are shown below. Keep in mind these icons are created in a vector-based application.
The video: https://www.youtube.com/watch?v=je1H-57AaVg
The creator: http://iconka.com
I see they are using Xara Xtreme which is still my favorite vector illustration application for the past 10 years.