The song " Oh You Pretty Things " was not directly linked to any website involved. But when i did a google search of the green ice image in Sean’s tweet, I got 6 results back.
One of the links was a review of Legion S01E06 on mymbuzz. com posted on March 16, 2017.
At the end of the review there is a section called " And The Random " where the reviewer lists this , “The incredible version of “Oh You Pretty Things” at the end of the episode is by Lisa Hanigan.”
The lyrics are interesting.