Here are some ideas from pinterest & google:
https://www.pinterest.com/pin/280630...41888/?lp=true
this one has brick walls:
https://www.pinterest.com/pin/525162006542716975/
https://www.google.com/search?q=joyf...w=1092&bih=610
Attic windows quilt pattern seems to be popular...but without walls around the 'window'.