I like Flooter for the gold because of the overall gray hue that is hit with splashes of color on just the right icons. The style of the icons and the gray bring it all together as a themed package, yet the "hits" of color make it exciting so that the package as a whole doesn't have the same look to every icon, which makes some packages kind of "blah."
For silver, I would choose Novacons. Looks very themed yet each icon is different enough to hold its own.
Bronze...hmmm...how about Cardinal (in any color). It is exceptionally well done but the icons get a little boring...they are not different enough from each other.
It's hard to be so critical on such great icon packages but I guess you have to pick them apart in order to make a choice as to which one is the better themed package. They're all winners in the general sense. (Good, I ended that by being politically correct!)