Concerning dead pixels i would try to take it back, although those pixels are small if you know where they are you will see them.
But a little question about the wall mounting. Thanks for the pictures by the way. Did you have to take the iMac apart? I'm asking this because it looks like you have to remove the stand it comes with and that looks bolted inside the machine.
So confusing this when i look at my back of the iMac.![]()
Check out this video: http://www.youtube.com/watch?v=Cmm7jWU-g2s
Few minutes and you're done