Ooh, very steampunky. With a texture that should look very nice.
Hmm, museum... A steam locomotive? A difference engine?
http://www.screensite.org/courses/Jbutler/T389/DifferenceEngine.jpg Might be a bit too difficult to model, though... How about an exhibit which has, for example, the King of Mars' shaving mirror, eyeglasses and shoes? The National Army Museum has some personal items belonging to Napolean, so it's not too far-fetched. And maybe a giant globe of Mars being carried on the back of the Prince? Like one of those Atlas statues:
http://www.1worldglobalgifts.com/images/Awards/AtlasAwardLG.gif
And perhaps some symbol of their hatred of the British Empire: maybe the axe that was used to behead Charles I?
Secretary of Unknowable Knowledge for the Rock/Dink administration '08