No more kitchen sinks!

 I'm running a campaign set in a mythic fantasy version of the British Isles, circa 860 AD. Due to the nature of the setting, there's many monsters and magic items that are restricted from use, and I absolutely love the effect that has in game. Given that I'm using a twist on a real world setting, the players immediately relate to it and have ideas of what can and should be done in the adventure, and by limiting monsters and items, I'm able to reinforce their suspension of disbelief.
  I think that adding too many elements from outside influences such as Tolkein's works, Conan and pulp adventure stories, etc., tends to shatter disbelief and revert players into a headspace where they know that they're just playing a game. Actually one of the issues running B2: Keep on the Borderlands is the baggage that creatures like Orcs and goblins bring, because they've been done so many times in so many other kinds of games.
  In fact one of my drives to play systems like Original D&D was its restrictions on player classes and races, and a lot of my advice for running spellcasters is to limit the specific spells that they have access to. I just didn't realize that it's better to limit all of these from a setting perspective and not a system one. That might explain the popularity of settings like Dark Sun and Ravenloft, which specialize D&D in their own ways.
  Rather than running a generic fantasy kitchen sink, I think its better to see the monster manual and spell lists as options that you must remove pieces of in order to fit your campaign. Most tables that I've seen just assume that everything that exists in the rule books also exists somewhere in the campaign world, but by creating a campaign world where some things cannot exist has conversely freed me up to run a more satisfying game.

Also as a side effect, using a map of historical Britain and Scandinavia has absolutely crashed my interest in fantasy maps. Fantasy maps are usually just pastiches of real world places anyway, with odd geography. I think it would be fun to run a campaign in Central or Eastern Europe as well, which would give access to most kinds of biomes.