Mhh, im not too sure if looking into other maps will lead to innovative new ideas.. rather think about new stuff.. most often the best ideas are those you have when doing something pretty different, like cooking, and then you come up with the idea:
Why not have my heroes use an aggro meter "heat", which fills up in battle with other heroes and every hero has his own unique aggro ability.. okay thats not very innovative at all, but would be rather new for a dota clone, maybe be better than in most other games an aggro meter is used.. (btw: i dont think you can come up with this particular idea when cooking, i was just short of any other ways to describe it :3)
Or maybe while doing some history research for university:
Why not add banners as a gameplay element.. in medieval times, banners and drums were essential to the moral of an army so why not add it as a gameplay element.. being able to set up a banner for buffs and being able to steal the enemies banner to weaken them..
2 ideas which just might come to your mind when not forcing to think about your map, doing your everyday casual stuff..