customize the style throught style.css ?

Hello all,
The Taxonomy Super Select module answers almost all my needs,but it remains a point:
I want to customize the display style during the creation of a contents.
I wish that the taxo box is displayed as a tree, such as the tree taxonomy manager module.
I would like for example removing the system of arrows and replace it with a '+' and '-'.
Does someone has already redefined the style to display a "tree" through the file style.css, and if so, could have an example?
I know, it makes a lot;)
Thank you in advance for your answers.