I’ve found the Nik Collection (especially the Silver Efex application) to be great for preparing photos for the Glowforge. There has been a few mentions about it here on the forum:
Google acquired it back in the day and made it free. Then they quit supporting it (so it works with adobe programs now - but no guarantee of it working in the future). Dxo then purchased it from Google and said they have been making some updates.
Apparently, those updates are now made according to the email I received. For a limited time, the plugins are available at a discounted price. Here’s more info: