jNice is a very useful jQuery plugin which helps you to create some nice forms from the html inputs. Unfortunately it is missing the customizing for the multiple select input, file input and textarea. I have modified the jNice script in order to enable the styling for the multiple select input. In the near future I will update to make it work for the input and textarea elements also. The example page for the updated script can be found at www.mage-contacts.com/jquery/jnice/ and also you can download the example as jnice_v11.zip. If you have questions regarding jNice you can give a feedback here.
The original site of jNice is at www.whitespace-creative.com/jquery/jnice/