How to cache background (website background image)?

Question

PHP

Greetings, dear connoisseurs.
What ideas are there to cache the background of the site, if it is written in CSS like this (first screen)? The code is already written in .htaccess (second screen).

Everything can be cached, except for the background pulled through the link. And this pull-up method should be preserved, because, as far as I know, it is the best and without artifacts. But how to cache the background, I can not find the answer.

body{

    background: url(/img/fon17.jpg);

<FilesMatch ".(flv|gif|jpg|jpeg|png|ico|swf|js|css|pdf)$">  
Header set Cache-Control "max-age=10368000"  
</FilesMatch>

The goal is to get rid of this (on the screen). And this can be done only by setting the cache lifetime for a given site background.

Answer 1

1) Google can also be wrong, check if this image is being served correctly by the server, go to the network, see if it stretches with the necessary headings, perhaps the data has not been updated in googlepagespeed ...
2) check the image extension, it may be written in uppercase , and in the rules you have a case sensitive regular season.
As long as there are no more ideas...