You are rubbing out the image because you are overwriting the definition here.
Background is shorthand for all the background properties and any properties not specified revert to their defaults. Therefore you are effectively saying background-image:none
You need to specify background-color:#E8F1FE;
to just change the color and nothing else.
Aletrnatively combine them into the shorthand as follows.
Hope that helps
background: #E8F1FE url(../images/bg.gif) repeat left top;