(Please note, this is an informal collaborative page.)
A Non Stereotypical Fantasy world is a World that is built or created with the conscious decision in mind of making it non generic. For example: D&D, and World of Warcraft are great examples of stereotypical fantasy worlds. It's almost strictly good Vs. Evil, Elves hate Dwarves. Dwarves mine and use gunpowder all the time, Elves live in forests singing to the trees. Dwarves are short, posses long beards, and its almost impossible to distinguish between the genders. Elves are lithe, fast and skilled while using their keen eyesight and amazing archery skills to shoot enemies from afar. The Men tend to have little on their side, yet always end up winning, and tend to have knightly charges. And of course we cannot forget the Orcs and trolls, and trolls, then especially the EVER present Dark lord. Orcs and Goblins are green, vicious and have diminutive strategical skills. Trolls simply like bashing things and have a brain the size of a retarded ant. Now the Dark Lord is the most generic of all. Look at all the Fantasy you've read. There's most likely a Dark Lord, evil god, or some sort of super powerful evil being. Even the names tend to be similar, besides the usual "Dark Lord" or "The Evil one" perhaps "The Forsaken lord", sometimes he's called something exotic like "Abbadon" but such names are few and far between, while always being similar to one another. And lets have a look at their personality, they're always angry at something, tend to look menacing in black spiky armor, and usually have an evil laugh (and in some rare cases where said Dark Lord is really outgoing, they actually want to be classified as "evil").
Low Fantasy is a classification of fantasy that is similar to a Non Stereotypical Fantasy World, in some respects. There is no narrative classification of good or evil, except for when the characters say it or the reader assumes it, and the use of "stereotypical" creatures is kept to a minimum, if not ever used at all. Low fantasy, as found in current literature tends to have a dark overtone. Not from some sort of impending evil, but from corruption, war and lack of unity or order in the presented world. A good example of this would be "Conan the Barbarian". Of course not all Low fantasy is like this.
Now of course we have to remember that while "we" are creating something that is non stereotypical, each piece will be different. Some will involve more generic material, while others will stick even more to the "Low fantasy" genre. Those which bend the furthest tend to be slightly dark, and gloomy, but not by default.