This is a string idea I got from the internet.  It was various black lines starting at the center and going to the edges.   The tangles I used are|:  #1 Steampunk Series by Molossus, Tri=po, Ving, Flooka, Printemps, and Betweed.  The colour is from some stamp pads I have.  I didn't shade this Zentangle because I thought it had enough colour and it looked finished to me.