Adding backgroundimage into articles, news, edito .....

You don't need to touch anything in the config,
you go to the admin, get to your article(the edito or the news)
you put CKEDitor in source mode) and use the DIV tag (the opening one at the beginning, the closing one at the end) like this :

[<div style="background-image: url(img/myfond.gif);">]
your text is here, bla bla bla
bla bla bla
bla bla bla
end of your article
[</div>]

Thanks to Tanet for this tip.

Don't forget to delete the brackets [] in first and last lines.

Updated 2012-02-21 Corrector