Our latest assignment in my photography course was called "Serial Typology". We had to take a series of photos where the subject of the photos was the same type throughout the series. For example, a series of photos where the subject is mid century ranch homes, or palm trees of south Florida.
Initially I thought it would be neat to take pictures of peoples feet, just a shot of their feet with lower legs. But I was way too embarrassed to walk around asking random people "Hey, your shoes are cute, can I take your picture?"