That last one is way cool.  I think the texturing on that model will make or break it though.  If you think about the use for that kind of pendant, it's not something someone would use as a common fashion accessory for any old character.  It's going to be an item someone will use on a wizard, or fantasy creature.  If you texture that thing as detailed as you modelled it, which I'm sure you will, it could end up being a great hero object, around which entire storylines could be played out.  If you just give it any old polished metal shader and leave it at that, then few people will have the foresight to see the potential in it, and it's not likely to be noticed.  That's assuming you're making it into a product.  I think the very center of it looks like some kind of weird eyeball.  I'll be interested to see what you come up with for that object.

It looks heavy on the polygons, but I don't see much room for cleanup there either, unless you're baking out the high res to normal maps.  Looks like just about every edge in that shape is being used to create the curvature.  If you reduce the poly count, I'd start by removing all backfaces that are hidden, check for coplanar faces and remove those (I'll bet you have a few in the middle there).  Looks like all the latitude lines on the hemisphere are beveled.  You can save a whole lot of polygons there, by baking all that detail out to a normal or displacement maps, and using a low poly proxy instead.

Interesting model.