How to set up icon in kickoff (plasma 6)

Help
1

Hi! Hope that some plasma-manager developers are here.

How can I set the icon for kickoff in plasma? To be more specific I want to change the first icon on the left:
kickoff-icon
and I want to use a .jpeg file. Is it possible to accomplish that?
I know about this option:

programs.plasma.panels = [
  {
    widgets = [ { kickoff.icon = com.some-system-icon; } ]
  }
];

But I can use only those which are installed with other applications.

Best,
Miro