I currently upgraded my system to Ubuntu 12.04 from Xubuntu 11.10, just to test the development of Unity environment. As I can see it, Unity undergone rigorous process of enhancements and improvements and as a result, Unity now is much faster, more responsive and new user-friendly.Unity will be my default environment from now. One thing I noticed after installation when I switch to Unity 2D environment, is that the icon size adjustment is not available.
Luckily, I was able to find a workaround over the internet.
1. Download the script from ubuntuone.com/0eanQDkYQUsygOqOqL8eX9
2. Make the downloaded script ‘executable’ (Right-click > Properties > Permissions > ‘Allow executing file as program’)
3. On the command line execute
cd Downloads sudo ./script.py 32
where the 32 is the size of the icon in px.
For the changes to take effect, log out and login back.
Reference: OMG Ubuntu