I think that challenging the perceptions of the players in this way is important. It makes the world more memorable as they rally an orc army to help defeat the goblins. They are currently negotiating with a tribe of minotaurs and will eventually be fighting/negotiating with a city of ogres of the right for a tribe of centaurs to live in the area. All of this while trying to prevent the hostile take over of the world from an army led by kobolds who worship dragons, as is typical of them.
This is not to say that every group of orcs in the world has become good. There is a chaotic evil nation of orcs waging war in a different part of the world, that my players and the general public know of. Same with the centaurs. The adventure comes from having to first convince people that these guys aren't bad like those guys, and then dealing with the repercussions of trying to end interracial blood feuds, carve a niche out of regular society to help everything work more cohesively and, in the simply try and have very one not kill everyone else.
This leads to many adventures ideas, and the players generally create them on their own, all I have to do is listen as they plot. When they debated a method to get the centaurs allied and peaceful with their own nations, they came up with a multitude of complications I would never have thought of, simply as they have a different perspective then I do as DM. I simply write these ideas down and flesh them out at a later date. It also leads to a lot of varied encounters, ranging from combat, politics, stealth missions and the occasional public speech. The variety helps keep the game from becoming stagnant, and I would never have to create the basic idea for anything if I didn't want to, the players generate enough content on their own.
So here is something that I think you should try. Create some form of problem that is to big for the players to overcome on their own, or with their regular allies. Drop some hints that an unlikely ally maybe found in one of the neighbors that the players would generally just slaughter, orcs are a good one for this. Have them try to get he orcs to ally with them and get the humans/dwarves/elves etc to accept it. As they plan listen to the complications they come up with and write them down. Also make sure that the orcs don't give in to easily, I mean the players must prove themselves trust worthy. Then simply flesh out a few of the complications in an imaginative way, potentially on the fly if you need to. Your game will be better for it if you can do something like this. Not to mention its always great to hear the Dwarf in the group go "Stay a way from my orcs".