In this design the longest strokes are transparent, leaving thick empty trails in a design otherwise crowded with curves.
I thought leaving gaps in the design would make it really clear which pieces border the empty strokes and provide a skeleton to work from, but the solid green pieces were the hardest to match up (in retrospect, a very obvious consequence), so solving the puzzle relied on finding the thickest pieces and working outwards from there.
Each jigsaw is designed and developed entirely in the browser. Above are some random outputs generated on the fly just for you – crack open the explorer for finer control of the parameters.