When there is more than one model state in Inventor file and there is unique part number for each model state you've got items for each model state. However each item gets the same thumbnail. It is understandable that in file, when there is only one record file for many model state it would be hard to distinguish thumbnails, but in items environment, when there are unique records for each model state it seems to be simpler.
Idea is to have different thumbnails in items created from different model states, because this model states can be geometrically different.
Picture in the attachment.