Here's the giant IAU 2012 sign outside the convention centre. Plus some SKA balloons (and someone's children!). ;) It was a busy meeting with the children accompanying us (my husband is also an astronomer) and attending an UNAWE run workshop during the first week (article about the workshop is online here) and also in the 8th Edition of the IAU Daily Newspaper.
The Korean Astronomy booth had the best takeaway models. You (well I) can build the below from a flat packed kit. My kids made during the day camp the moveable models of Magellan (which we also had fun destroying to pack to bring back to the UK). These were really impressive.
There was also the below, full working replica (on a slightly smaller scale than the original) of an ancient Chinese water clock. This was the first clock in the world able to keep accurate time. And it was also beautifully carved.