Hello 
,
I monitor my apache log in case something fishy happen.
I saw that someone (or a bot) queried my server for the file icons/sphere1.png and my server responded with the png. So this file is in my server for no apparent reason.
There is no issue with that in itself but I want to find out why it’s there and maybe get rid of this useless file (and others if they exist).
Someone know the why is this file on my server ?
Thanks ! 
This file respectively the Icons directory belong to the Apache HTTP Server. Apache serves these files by default via an alias and uses the icons for things like directory listings, error messages etc… So nothing fishy happens on your server and there is no security issue.
If you want to disable the icons or the alias completely you can comment out the corresponding lines in /etc/apache2/mods-available/alias.conf. (This path is applicable for the default configuration of Apache on Debian and Ubuntu and might be different on other operating systems.)
That worked like a charm.
Thank you for your quick, instructive and clear answer