I've updated my pet project about major medals earned by gymnasts from different nations in gymnastics. You can check it on Wikipedia here. I was finally able to find all of the results from all of the World Cup events in artistic and rhythmic gymnastics since 1983. It took me, like, 5 years, but it's finally done. I'm slowly updating the corresponding articles about the World Cup series with all of the results. The one about rhythmic gymnastics is complete, but I still have to upload some results for the artistic gymnastics one.
Probably the most surprising information about the World Cup series are medals for Serbia, Algeria, Panama, Syria, Jordan and Thailand. These are not countries you usually associate with gymnastics. Serbia, in special, is very nice to have on this list, since they earned a single bronze medal at the Artistic Gymnastics World Cup in 2006, and I'm not quite sure people in the country know about it at all.