Allow me to join in the "I was gonna report this, too" conversation. This occurred in Team Builder, because Snow Orianna. The first two games did work, but after that, well, they didn't, and seemingly for almost everyone.
Here's my Twitch broadcast and a screenshot, though I always exclude the launcher and main menu, if you will (because they keep getting in the way of the in-game video and I don't know why, but yeah). The first game, the skin did indeed work. The couple afterwards, nope.
Immediately at the beginning of the video, everything's cool and Snow Ori shows up. But the problem can first be seen at 36:40, and it happens two or three times after that.
Er...Hang on, never linked a video before
At first I assumed it was my own fault, but I made absolutely, 100% sure the next game that the skin (in my case, Snow Orianna) was selected. I even swapped back to the default, selected that, left the selection menu, then opened it back up and re-swapped back, to act as a kind of reset. I tried twice with the same results. Totes confirmed, but this happened then.
None of 'em worked. For anyone. Lux in particular was hilariously upset (Lux's skins rule, admittedly), as were the two guys I was queuing with. No PROJECT: Yasuo or Pool Party Graves for them then, and it was the third time it happened.
Of course, I asked in-game if others were having the same problem, which was confirmed.