Change background of MusicVisualisation

Hello!

I’m doing my first steps in Skinning, made a copy of the skin Estuary and now I’m trying to change a few things, just for practice. Some changes worked well (replacing and resizing cover images and fonts) but it didn’t found out how I can change the background image of the MusicVisualisation with an image stored in a new directory. I tried it with

but that didn’t work. I couldn’t find any information here if the use of special:// is also correct in Kodi 17 – maybe it isn’t. I’m working with a Linux Mint OS.

If anyone could help me please..?

Thanks
Harry