Here is the photo reference I found online:
And my final portrait done using the pen tool in Adobe Illustrator:
It took a lot of time, but I am really happy with the final result. I never thought that I would have the patience to do an illustration this detailed using Adobe Illustrator.
Lesson Learned: When working digitally, give yourself time to take breaks!
I worked on this portrait for 8 hours straight one day, and that was a bad idea. The prolonged sitting took a serious toll on my back and shoulders, the constant mouse-clicking gave me cramps in my hand, and the intense focus on the computer screen resulted in infrequent blinking, which dried out my eyes. One of my contacts actually fell out of my eye without me even touching it because it got so dry! Even then, I was too focused to get up and just stuck the contact back in my eye without a mirror. Bad idea.
When working with traditional mediums, I have to take breaks to wash paintbrushes, sharpen pencils, get more supplies, or whatever else I need for the project I'm working on. But for digital work, there is no reason to leave the computer, so I just got sucked into this mode of serious concentration and I didn't get up from the computer at all the whole time. Now I know that I need to stop and get up and stretch every hour or so to give my body a break!