add background image to themeroller theme

Question

I am new here and I search for a solution but diddnt find a solution.

I am working on a web app with T/roller theme and I need to set a background image to over ride the theme swatch I have it working with the following js but the swatch colour shows for a second before the image shows, image is called on page load I need a way to override to theme

 $('div[dsid="logincontainer"]').css('background-image','url("' + Tiggzi.getImagePath('FolderSwitcherBG.png') + '")');
$('div[dsid="logincontainer"]').css('background-size','cover');
$('div[dsid="logincontainer"]').css('background-position','center');
$('div[dsid="logincontainer"]').css('position', 'absolute');
$('div[dsid="logincontainer"]').css('width', '100%');

I suppose the question I am asking really is, is there a way to add an image to the theme that will over ride the swatch colour.

thx for reading