How to change backgroung title image

[leksand]

hum, that's a good question...

List of CSS Files i have :

bootstrap.css
flexslider.css
font-awesome.css
post.html
templatemo_misc.css
templatemo_style.css
templatemo-slider.css

I'm working on local now, so i can't check whether it is the reason or not...
Thanks for your help anyway!