I want a background Image on my Application Menu and Taskbar

I want to put a background image on my Application menu (The menu that pops up when you press the Meta key) and the taskbar (i believe its called a Panel in KDE), right here:

I tried editing the panel-backround.svg file in ~/.local/share/plasma/desktoptheme/theme-name/widgets/ to have the image as the background, but that didn’t work. What else do I try?

Make it transparent - then you get a desktop background see-through