Changing icons on Widgets

Hello,

I need to change the icons of the sidebar, I want that Instagram widget shows an instagram icon (I modified the sprite [http://palmaentumano.es/wp-content/t...ns-0090d3.png] and I use this like a background on widgets.css.

I only get the star icon on every widget despite I indicate on widgets.css this:
Can anyone help me, please?


You can see more at www.palmaentumano.es

THANKS!