Email background image

I would like add background image to mail email. When i test on MailChimp, the preview is good (with inline style and minified).

But if i run test on my mail (Gmail APP and Outlook), i've no background. If i open the mail in browser, my background is show.

I've test with this :

background="http://domaine.com/myimage.jpg"

and

background: url('http://domaine.com/myimage.jpg') !important; // Inline style

No result. Anyone have idea ?