I ve struggled with picons since Tvheadend 4.2.
I finally installed smaller picons on my server, disabled image cache and so on. And it works, but not on all clients.
They just refuse to appear on Kodi 17 on libreelec beta 3. Client version is ; 3.4.13.
Getting crazy, I decided to install the tvhclient on android and voila all picons appear nicely.
I therefore conclude it is something on the kodi side which does not retreive them from the server.
I can see them by http:ipserver/imagecache/500 for example.
Anyone eles experiencing this?