Best USB hub to match the Thunderbolt display?
There's always the various Mac mini stackable USB hubs - those usually look pretty nice.

If you can't find a hub you like the looks of, you could always hide it:


A shelf that goes on the monitor stand to hide items behind the monitor
Or you could just tape (or velcro, thanks to @jaberg) the hub to the back of the monitor to keep it out of sight.