I know that there's no canon, but there is what the Homestuck fandom has taught me is called headcanon — that is, your personal image of the universe of a book or whatever.
So, have you come across anything that rings a Foundation bell for you? If you haven't, but want to try looking for something, might I suggest BLDGBLOG?
This is shameless reference-mining on my part for a personal project, a good way to get out of my personal 'shadowy clinical institution' visual cliches, but I figure it could be a fun community discussion as well. What do you think?
edit: note that this is different from visual creepypasta, in that I'm wondering what the more mundane aspects of the Foundation look like in your head(s). Is it a massive cyclopean institution like Aperture Science in Portal 2? Is it a small, cramped, dusty research outpost? Is it the arctic research laboratory from the Thing or that X-Files episode? Do people blink when Kain walks down the hall, or is (he/she/it) forced to wear a doggie hijab to disguise their true form?