it is just a code that changes the background,
i added the code in admin - user profile settings so if our members want to change the background they just have to add the image url to the code i provide them, it is no different than adding a html code to add a graphic or embed code to add a youtube video,
our members enjoy customizing their pages adding graphics, music players, videos, changing backgrounds,
this is the code i use - note it works in origin and showcase, it does not work in macabre or darklets theme, my site uses origin, i have another code which works in crayon and basic,
i dont know enough about css but if anyone does and can provide a code which works in all themes .........
you just paste the image url where i have written add image url here
<style>.ow_page_wrap {
background-image:url('ADD IMAGE URL HERE');}
</style>
it has not been tested in all themes,