It's fun to use strings and just go with it. It's even more fun to me to use mono tangles where I only use one tangle pattern for the whole piece. I find it so relaxing to just keep going.
The first tile uses 'Striping'. As you can see, this is a great tangle to add shading to. 'Paradox' is the tangle in the lower tile and I just changed the colored Micron pen I was working with in each section of the string. I did my shading with colored pencils. I thought it was too heavy though so I (GASP) used an eraser and was left with a very light shading that I was very happy with.