you can install default unity by installing ubuntu destkop in software center
and then removing lubuntu (e.g for 12.04): http://www.psychocats.net/ubuntu/pureubuntuprecise

another option is to use minimal iso found here: https://help.ubuntu.com/community/In...tion/MinimalCD
and then install ubutnu desktop. here is a tutorial with icewm (just replace icewm with ubuntu desktop package ):
http://www.psychocats.net/ubuntu/minimal