L-systems (varav.in)

I've also toyed with L-systems.

I made a little gallery with some of the more interesting ones I came across: https://ehq.com/lcurves/

Obligatory reading on L-systems:

http://nothings.org/gamedev/l_systems.html

Interactive Javascript L-System: http://davmlaw.github.io/ProceduralGraphics/lsystem4.html

Here's something I made using L-Systems:

http://martijnbrekelmans.com/lsystems/lsystem.html