At my Doodle Drawer app, I’ve played with a couple of “brushes”. The idea is to treat the connection lines differently.

shadedshaded
sketchedsketched
furfur

Basically the difference is that the line connections are drawn closer or further away from each line based on the formula of Harmony.

The ‘shaded brush’ looks like this:

The sketched brush looks like this:

And the ‘fur brush’ looks like this: