One of the oft-misunderstood taglines of the D&D setting Eberron is that everything in D&D has a place there. Of course, that doesn't mean that everything in D&D is in Eberron, like some crazy goulash, but it does mean that if it exists in D&D anywhere, there's a place in Eberron where it can logically fit. A nice concept.
One section of the setting, the continent of Sarlona, is a bit different. For most intents and purposes, you could almost treat Sarlona as a separate setting entirely, one that's at best only tenuously connected to the "main" setting, which is the continent of Khorvaire (with the Xen'drik annex, maybe.) And Sarlona is built on a very different model, and one which I quite like: the idea of picking only a handful of unusual D&D elements to create a setting that utilizes D&D material, but doesn't feel very much like D&D. In large part, this is because of the notable things that it lack, but that's part of what makes it fun.
For instance, the population of Sarlona is mostly human, but when it's not, you don't get your standard elves, dwarves, halflings, orcs, goblinoids, etc. Instead, you get a sizeable number of shifters, some changelings, ogres (and ogre magi), skulks, kalashtar, and a culture of duergar and dwarves that are well integrated with each other.
There are little (if any) of the standard magic-using classes around; instead we have psionics to give us the wahoo factor. A lot of D&D players don't dig psionics; they feel too "science fictiony" to belong in fantasy, but heck; that's a big part of the attraction to them for me. Most of Sarlona is ruled by Imperial Riedra, a giant nation that is highly stratified, populated by religious fanatics, and secretly under the thumb of nightmarish creatures from another dimension. Kind of like Star Wars imperial menace combined with some H. P. Lovecraft. An obvious campaign idea is having the PCs be "part of the rebel alliance" that struggles to overthrow or at least mitigate the spread of this Empire.