[curt.clifton]

Right.

My workflow for script icons is to draw the icons in OmniGraffle, typically very large. Then I export to a png, adjusting the scaling to get a 512x512 image. I drag that image on to a new Icon Composer document to get an icns file. (Icon Composer is installed with the Developer Tools from Apple.) I drop the icns file onto the Icon Droplet application to get an "application" file. I can copy from the info. pane of that file and paste onto the info. pane of my script file.

There's probably an easier approach, but this one gets me icons that seem to scale nicely.