One thing I use to love about Melbourne was you could often get your hands on free postcards. They would be at cafes, local library, information centers or randomly scattered at points around the city. It was usually a form of advertising, with designs frequently roaring. I use to always pick them up to use in the classroom. One nifty use was to group students. I would get a different designs and cut them into pieces. In class each student got a piece and had to find their group.
I use to like them as they had bold colors and designs and were made of study card so you could reuse them easily. Now I can't get my hands on them, and lift images off the net. There is one major advance is that I can choose images to link with the content - so once they have their groups they can turn and talk to their peers about why i chose that image and relevance to the topic. However, unless I get them laminated, usually its a single use resource. I find its always good to sometimes use something like this to mix up groups randomly.