I was reading a thread on spiceworks regarding IT pranks. Among the comments I found this interesting link:
http://www.ex-parrot.com/pete/upside-down-ternet.html
It uses IPTables and Squid to distort images in a web browser, either making them blurry, or flipping them upside down.
This example at a glance looks fairly simple.
Could something along these lines (but more complicated) be used to do content blocking like ublock does?
You could then theoretically use that type of un-parsed list, and some static blank image files to proxy.
My brain is likely over-simplifying things. I just wanted to put this out there.