TITLE: partly obscured Rubik's cube
QUESTION [8 upvotes]: I just came back from a beach which features a large Rubik's cube (2m high).  The base of the cube is not visible and the top is not coloured. The four vertical sides are each divided $3\times 3$ into coloured squares as they should be.  I was idly wondering: how can I tell if the patterns appearing on those four sides are actually possible for a real cube?  Clearly there are necessary conditions like having at most 6 different colours and at most 9 squares of each colour, but is that sufficient?  Can the legal configurations be characterized?

REPLY [10 votes]: Is this your cube? 
http://www.redbubble.com/people/yolanda/works/6358896-rubiks-cube-at-maroubra
If so, it is not solvable. The dark blue (grey?) and white centred faces are opposite each other, but there is a corner with both colours.
Edit: the linked site's interface changed slightly, so now the two images are on different pages. See here http://www.redbubble.com/people/yolanda/works/6351863-surfing-fun-at-maroubra-beach for the alternate view showing the corner.