Is there any way to change what display style is used with the
growlnotify command line utility? I don't want to change the default one, just the one that is used for that instance of the command.
You can, however, create an AppleScript application/script that uses the Growl API to issue different types of notifications, based on some parameter. Growl documentation on how to access it via AppleScript.
Here's a sample script for AppleScript Editor:
"1" and "2" are the names of the supported notification types. Run this script like this:
Parameters are (in order) notification type name, title, and description.
After running it once, you can configure the display settings for the notification types in System Preferences.