You can drop any LGA1156 CPU into that board, and it should work, though there's a possibility that the more power hungry ones (e.g. high-end i7's) might cause instability due to weak power circuitry on the board. I'd probably give it a try anyway.
Some CPUs to look at:
Core i7 860/870/880
Core i5 750/760
That said, even the highest-end i7 for your board is still going to be close to a decade old, and weak by today's standards. There is no CPU available for your board that will not cause slowdowns in any modern games.