The closest firmware to the Android 4.0 you can get for Galaxy S in 2012 is this latest leak of Android version 2.3.6, this firmware comes with Android 4.0 Ice Cream Sandwich features like Face Unlock, New Android 4.0 lockscreen, Galaxy Note’s Photo Editor, Galaxy S2 video editor and overall snappier device performance. Samsung has already announced that they will not be releasing Android 4.0 ICS for Galaxy S as it will only be getting this Android 4.0 value pack because of lower device specs, so get your hands on this official ROM and install it. Download the official XXJVU firmware for Galaxy S from the link below.
Download Android 2.3.6 XXJVU for Galaxy S (Android 4.0 Value Pack 2012)
Download link | Filesize: 226 MB | ZIP file Password: samfirmware.com
How to text and video tutorial for installing Android 2.3.6 xxjvu on Galaxy S is now available:
Tutorial link along with Video of installation.