Regarding non-core monsters: the question I as judge would ask is, "If X is found in Y, is it plausible that we're unlikely ever to encounter more of them?" If you propose an infestation of some kind of monster that threatens to overrun the world, that's something we'd all have to deal with, and if the monster isn't found in the SRD (or at least in the Monster Manual), we can't. But if your adventure revolves around a single specimen of some really exotic creature found somewhere north of Rivenblight, well, that's not going to establish anything that would tie anyone else's hands, so the creature could be just about anything.
Now, as far as published material: an adventure needs to be approved by two judges, and judges have complete latitude do decide how much they need to know to approve. But let me cite as a warning what happened last time we had such a proposal. One judge immediately declared he was fine with it, sight unseen, because published modules from major game designers are as a rule well playtested. The second judge (me), insisted on more information. I got a list of encounters and treasure, and against my better judgement decided to accept that, without any information about how it would all be strung together. All was well, until the DM disappeared. I, as judge, am now runing the adventure, and doing it by the seat of my pants. In retrospect, my advice to my fellow judges is: do not approve an adventure unless you know enough to take over the helm in an emergency. I know I wouldn't. (Well, I might offer the second approval if the first judge to approve also pledged to judge the adventure and reassured me that (s)he could take it over if need be.)