Procedural Prefab preview possible?

Pardon my alliteration :)

I have a script on some of my prefabs that creates the game objects with mesh&renderer components at runtime. But the preview icons for these prefabs, such as in the project browser, just show up as cubes. I'd like my artists to be able to more easily tell what kind of objects they are working with beyond just the names.

Is it possible for my script to create the image to appear in that preview window? Or is there a way to attach an image that will be used as the preview for the asset which doesn't impact the runtime? We are using Unity Pro if that's relevant.