i want to add footer background image in bartik subtheme

some how when i add image url to footer it doesnt work but when i add to footer wrapper it works! i mean i am able to see the image

This is first subtheme i making , any help will be highly appreciated!

/*manual background changes*/

/*OVERRIDE regions[header]:  setting region background color to transparent so that you can see the background image behind it*/
#header{
  background-color:transparent;
  background-image:none;
}

/*OVERRIDE regions[content]:  setting region background color to transparent so that you can see the background image behind it*/
#page,
#main-wrapper,
#main-menu-links li a.active,
#main-menu-links li.active-trail a {
  background-color:transparent;
  background-image:none;
}

/*OVERRIDE page-wrapper:  setting a background image*/
/*change ONLY this one for full screen images*/

/*OVERRIDE regions[footer]:  setting region background color to transparent so that you can see the background image behind it*/

#search-form input#edit-keys, #block-search-form .form-item-search-block-form input {
    float: left;
    font-size: 1em;
    height: 1.143em;
    margin-right: 5px;
    width: 9em;
}

.region-header .form-text {
    background: none repeat scroll 0 0 rgba(228, 235, 220, 0.7);
    border-color: rgba(228, 235, 220, 0.3);
    margin-right: 2px;
    width: 120px;
}


#footer-wrapper {
  background-color:transparent;
 
}

#footer {
background:url('green.jpg') center ;
}