The last Docker image of guacd has a size of around 400 MB. If you use Docker image debian/stable-slim as base for guacd, the image size is reduced to a total of 330MB. This change (PR #222) is minimal, but has a big benefit. It reduces the final Docker image size.
My comparison is based on the latest public image.
REPOSITORY TAG IMAGE ID CREATED SIZE
guacamole/guacd latest 57f6ce568e0d 3 months ago 395MB
intern/guacd latest e562a8exf0x2 2 days ago 327MB