No, as this script needs user interaction (and Smart Rule scripts run automatically).
This Smart Rule script sets a thumbnail. Should be easy to adjust it to your needs.
As you’re into customizing thumbnails you’ll probalby also want to take a look at Script: Colorize DEVONthink Icons (Color Code Magick).
For me it’s one of the most useful scripts as it makes finding groups (e.g. in the navigation sidebar) a lot faster. Instead of searching for the name it’s just one look and I know “Ah, this is what I want”.