The front of the medal always depicts the same imagery at the summer Games – the Greek Goddess of Victory, Nike, stepping out of the depiction of the Panathinaiko Stadium to arrive in the Host City.
Explanation of the back's design:
The curved background implies a bowl similar to the design of an amphitheatre.
The core emblem is an architectural expression, a metaphor for the modern City, and is deliberately jewel-like.
The grid suggests both a pulling together and a sense of outreach – an image of radiating energy that represents the athletes' efforts.
The River Thames in the background is a symbol for London and also suggests a fluttering baroque ribbon, adding a sense of celebration.
The square is the final balancing motif of the design, opposing the overall circularity of the design, emphasising its focus on the centre and reinforcing the sense of 'place' as in a map inset.
The back does look a bit odd, but it's unique. And I guess that's kind of the point: to come up with a medal design that is 1) unique to the host city and 2) unlike any medal design that people have seen before.
I like the curved line amongst all the sharp angles and straight lines.