everytime I do a reboot I need to replace authSig behind the link of images I want to use. Perhaps I do not know how to make images stay in place in Lovelace dashboard. Below is an example of what is current. I would like to know how to make it better or add this feature.
You should be able to access it with just:
/media/local/pics/warning.gif
From within home assistant.
+1, works perfect this way, I do it for some TV channels icons stored locally in HA 
ok - it is not working for me as " /media/local/pics/warning.gif"
it works if I add the ?authSig=xxxxxx. examp = “/media/local/pics/warning.gif?authSig=xxxxxx”
I found my issue:
with playable files we can do all the suggested things previously.
But, with files like pictures, we have to create a www folder in the config folder https://www.home-assistant.io/integrations/http/#hosting-files
Then use http://your.domain:8123/local/audio.mp3 or for me it would look like http://your.domain:8123/local/pics/warning.gif
This is now working for me. Thanks all!