Personally I never worked with multistate objects, nor (hardly) with AS, but the OMV Help still can come to the rescue.
Your Multistate object may contain a collection of Images, under the property name 'images'. Each Image in turn has an itemLink property, which is of type Link. A Link in turn has the property filePath you are looking for.
This is in JS notation, not AS, but it shows you a path to investigate.