[jQuery] Css icon image in tree jquery plugin

File: jquery.treeview.css

Hi,

i would like to modify the css to visualizze other bigger icon of 30px
height 30px width; I know i have to add the path and the image in

this way

.filetree span newclass {background: url(images/image.gif) 0 0 no-
repeat;}

but i would like to visualizze them bigger.

Do you know?

Thanks