my samsung galaxy s2 gt-i9100 totally formatted or wiped. how to fix it. How to install new ROM
Go to this website and follow the Odin method to install a new ROM. You should be able to put your phone in download mode/Odin mode to do the same.
Try this out to replace to a stock ROM - http://android.sc/update-samsung-galaxy-s2-i9100-to-official-ota-android-4-1-2-vjms3-jelly-bean-firmware/

You can visit this website to find some nice ROMs for the phone with reviews as well - www.galaxys2root.com