Themes

1. A yellow car.
2. An abandoned building.
3. Someone with a bald head.
4. A photo showing three generations of people (need not be from the same family, but let's make it that there is at least a 20 year gap in ages to make up one generation gap).
5. The tallest building in any particular city.
6. A shot with a strong element of motion blur.
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See http://www.trekearth.com/read.php?f=1&t=11880&m=25655 for more details.