Icon not showing

First of all, hello ,
I would currently like to use icons.
There are two places here where you can use them. Unfortunately these are not displayed at all :c
These are SVG files.
Enclosed a screenshot.
But I don't think that one icon works anyway. (It is also not documented). But state icons should actually work, shouldn't they?

It must be jpg or png files; the plugin can't handle svg files.

Okay, thanks for the answer .
Then I have to convert all the icons once.