Hi everyone !
Yesterday, I saved LibreElec (7.95.005) using the LE configuration plugin, to install again LE on my sd card ( /flash was still 256Mb and I wanted it to be 512Mb, old setup, nevermind)
When I restored the backup, I noticed my picons directory was empty, meaning I lost all my TV channels icons. I just have now to recreate them again. A it frustrating for me, but I should have take more time before formating my sd card 
I'm not sure it's a "bug", but I wonder why the picons directory is not under /storage/.kodi/userdata rather than directly in /storage, or why it's not saved, because IMO, it's pretty much config than pure data (as video, pictures or tvshow if you see what I mean), don't you think ?
For now, in order to save my icons, I'll change TvHeadEnd setup to place all my icons under /storage/.kodi/userdata/picons, but if this post can make you change the paths or save the picons directory, maybe it can save time for other people 
All the best.
Smeulf.