I have a file of icons collected years ago (on Windows) and picked this funny one for the Menu on my panel. Of course any photo works not just icon files. This is Mint 18.3 Sylvia. It is using Transparent Panels app. The background is a Sylvia wallpaper. The icons frame is transparent too. I added the default Menu for comparison.
The text is needed to expand the size of the button but can easily be removed.
EDIT: Switching to a new icon for awhile. The Menu title is showing because the cursor is hovering there. The panel is at the top of the screen.
