https://www.quilterscache.com/A/AtticWindowsBlock.html is a classic attic window block -- free pattern website.
There are a couple old links here in the quilting board for bay attic window quilt, too.
Bay Attic Window with a panel. has a picture and a references to Ellen B.
And a great pininterest site for ideas
https://www.pinterest.com/wilhelmmjjm/attic-windows/