I'm just putting this idea out there, wouldn't an M33 inspired XMB theme be nice? In place of a wave we could have twinkling stars on an image of the M33 galaxy. Icons might have a "spacy" look or similar. just a thought.
Or maybe we could convince members of Team M33 to post up screendumps of their XMBs (with links so we might use the same theme). I think it would be nice to see what look they like for their XMB.