Hi,
To increase the size of the icons will appears when you click on the K button on the desktop :
- open the kde control center (click on K menu and then on the control center icon).
-click on "Apparence and Theme" and on "Fonts" on the left side of the window.
- on the right side of the window : click on the "choose" button of the line called "Menu"
- a new window will appears on the screen, and you can select the size of yours Kmenu icons.
Regards