I had a short visit of Bremen at the occasion of visiting Prof. Jahnke's group.
Before catching the ICE back to Munich, I could visit the cathedral and its Dom-Museum, meet die Bremer Stadtmusikanten and enjoy the old main square.
I haven't had time to take pictures, but Mikhail Glazov took very nice shots at some other occasion [1] which are how I remember the city.
A very nice place, to visit again!