Compatible XF Versions:
This is a simple add-on that'll change the page container for banned users (whether their account be banned or their IP be banned) to a very minimalistic page.
Practically everything is stripped out, with only the viewport, title and the banned error message remaining.
If you want to see how it feels to be subjected to this highly minimalist display, login to XF Liam - XenForo Add-On Development with the following details:
(You'll have to erase your session cookie [xfliam_session] to logout - XenForo doesn't let banned users' logout for some reason...)