Actually, if the icons differ visually you can always use an image collection to define a set of related images to use within your script. This is actually the recommended approach to use when you have two different images on two different machines that need to be used for a single command.
An image collection is just a folder of images that contain acceptable variations of the same thing. The nice thing about this is that your script can just reference the folder name and Eggplant will use whichever image that it finds first within that collection to execute the command.
Btw, this applies to Eggplant version 4 only. You can read all about “Image Collections” in the Eggplant Ref manual.