This is an interesting question, my first reaction is why go to the back if you want to avoid the ground...assuming the guy has some idea what he's doing, thats not going to be the easiest position to take and lends itself more to grappling than striking IMO. Sure there are good targets, but holding the back position and striking at the same time while standing seems tough. If I found myself there I'de go for a rear naked or maybe see if I could choke the guy out with his coat or something. If he defended that well, I might try to pick the guy up and slam him.
Finally someone understands the conundrum! While the back seems advantageous, the second you release your grip on the person to strike, they can maneuver away from you. Even kicks to the back of the knee, aren't guaranteed to be effective if you have a tight grip around your opponent -- the leverage isn't necessarily going to be there. And striking to the head, against someone that is leaning forward and bracing themselves against a suplex is futile.
I want moves that will work on anyone -- not just an unskilled opponent that is happy to stand erect, facing away from you, while you hit him from behind. After spending several hours, conducting a variety of tests with various sparring partners, here are the best moves I could find against a trained, ucooperative opponent from the back... which still enable you to stay off the ground.
1. Slide both arms downward and pull both knees towards you, while simultanously pushing upward with your chest against your opponent, pusing him to the ground.
2. Drop down and reach your right arm in front of your opponent down between his legs. Reach your left hand from behind through his legs and grab your own hand. Lift your opponent up and twist to the right while pushing your shoulders forward against him, throwing him down.
3. Lift your opponent, if you can, like you're going to suplex them, but instead drop them on their side.
4. If you have one arm in an overhook (perhaps after an arm drag from the clinch) stay behind and to the side of your opponent. Grab his other arm with your free hand. This position enables you to control your opponent, while freeing up space for those glorious knees.
Again, all of these moves enable you to either throw your opponent to the ground, while remaining standing or put you in an extremely favorable position to set up some devastating standard attacks.
I encourage you to try this drill out. It's not as easy as you may think to finish someone off with [insert deadly move here], if the person is uncooperative.
If you come up with some better moves, let me know. The back can be a safe place to be and an avenue to winning the fight.