I've never seen anything that good at a shoe store. A couple upskirts, not even racy panties, never mind none.
But I was at the opening of the first Sephora store in NYC. Big party, free booze. 5th and 50 something.
I was amazed to see that they had mirrored panels on the floor right near many of the counters. Naturally I managed to position myself properly and was rewarded with a fantastic white cotton panty upskirt. Not normally my kind of underthings but it was a great view, particularly because the place so invited it. She was clearly aware of the mirror, but didn't want to pull herself away from the social opportunity (talking to whoever). And she totally caught me looking, and was mildly embarrassed, but as I moved away, she stayed where she was.
I have no idea if they still have the floor mirrors at Sephora, but they sure don't at the one in my local shopping mall.