With the release of Android 4.0.4 to the Open Source Project, custom ROM developers have begun the scramble in working all of the newest features into their current work. One of the more well-known developers, Roman and his team from the Android Open Kang Project, have released Build 29 for the Galaxy Nexus and there are also builds floating around from other mentionable developers, inlcuding a stock 4.0.4 build from Birdman.
AOKP Build 29 | Stock 4.0.4
For downloads and flashing instructions, just click the thread link you wish to read up on and go from there. But do note, that when flashing a newer version of Android, you must wipe data/cache in order to have a clean install. We don’t want anyone bootlooping when trying to perform these tasks.