Depends on what you are going for. Here are a few examples...

On my first XF, since the wheels were so full (not too open to see through) like yours, I went with something that would blend and not scream at you, silver.



It kind of bothered me that you could not see them well, even at speed. With the new coupe, I decided to do wheels that would set off the calipers much more, and I painted them an orange/red hue that I liked.



What I like most it when I am at speed, and you can see those beautiful things staring at you. Lots more people are noticing them as well. With your black wheels, I think something kind of loud might be cool, but as others have said, you need to add other details or paint things to tie it all together and not make it look like you are just adding random colors wherever, more of a theme.

If you can not tell, I LOVE the new AMG setup