Things you should know:
1. there is a lot trouble involved if you use imagecache pls don't use it for local stuff (deactivate and clean)
2. Tvheadend 4.0 has a few bugs at this area
The simplest way to make it work:
- install Tvh 4.2 from addons (update from 4.0->4.2 will not work)
- copy your picons to the networkshare /Picons (snp to the vdr, srp to the tvh folder), reboot, ready
If you are unsure what you need downloads -> srp-full.220x132-220x132.light.on.transparent_DATE.hardlink.tar.xz or/and snp-full.220x132-220x132.light.on.transparent_DATE.hardlink.tar.xz (you could use both at the same time)
The Picons downloader is not yet implemented due major bugs in Kodi add-on system which prevent this