Well...the fact that they are overheads, you usually get some "air" as part of that setup, and if there is any kind of life in the room, you also get some ambience....if there is not enough, then raise them higher and/or change the room...or add some reverb when mixing.
Where do you place them relative to the kit?
My OH mics are only about 7' off the ground and the room isn't super-live (carpet on the floor, some ceiling treatment to reduce flutters...and my OH mics still have plenty of natural ambiance, I never add anything more during mixing.