Today, while nattering about without discipline or focus, I happened across the Book of Deer. It's classed as a Hiberno-Saxon illuminated manuscript - the "insular style." It may be the earliest surviving manuscript produced in Scotland.
More to the point, the evangelist portraits look like this:
That may actually be within my artistic talents.
The whole manuscript is online here. There are spots where you can see the illuminator started to fancy up some of the knotwork and then stopped...