The IntelliStar must not be getting the signal to change the image in the internal database. With my little exposure to the IntelliStar (and very minimal, I must say), the system will download the background files when sent over the satellite. From there on out, the STAR would listen for commands to use the specified background. The XL would work in this way as well, so there is no doubt in my mind that the IntelliStar is this way as well. In fact, I am 98% positive this is the concept used.
With that being said... it is most likely that the STAR isn't getting the command, or for whatever reason it isn't being properly written to the database to use the other backgrounds. TWC would have to look into it.