I had a thought that Alphonse Mucha’s work would engrave well, he did lots of art nouveau posters. So I googled for one of his paintings:
A quick test, cropped and adjusted the curve to make it a decent candidate for engraving — maybe all of 5 minutes to get it set up:
Not to get into settings too much here but, on Baltic, with “vary power” engrave mode. It’s amazing what you can do so quickly with the Glowforge.