CSS Image on background and texte

First sorry for bad english, not my native language. I try multiple way, but nothing that works.

I want to transforme my list (which are actualy boostrap alert) -> before

into list with an image and center text like this -> after

I try with background-image CSS property, but I can't manipulate size of the image used. I try also img and text on a div in HTML, but doesn't work eather. And that need to be responsive ^^

Thanks for help :)