Misposed upskirts
 

In a big way this falls more under the upskirt/downblouse category, but I'm interested in an ENF-related angle: Photographs where the woman is posing, or at least well-aware that she is being photographed (one posed shot justifies the rest of a set), but not flashing. That is, she did want to be in the photograph, but did not want her underwear (or lack of) on show. A potential for embarassment hence lies in that she is more likely to be embarassed if she flashed on purpose, and more likely to see the photograph herself, and perhaps to know that someone she'd particularly hate to see it, will do so. For this reason, the more formal the photograph the better (sitting for a corporate group photograph that will be put on your office wall or a newsletter is probably has a further distance between outcome and intent than if you're at a drunken hen-night playing with a novelty penis).
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That was meant to be, more likely to be embarrassed than if she flashed on purpose.

Lots of bridal shower and birthday pics elicit this type of picture.

these fit I think

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