So you want your program to be loaded INSTEAD OF normal things of KDE, as the ┐!┐plasma-desktop?!?
plasma-desktop is the program that shows the bottom bar, manages the KDE background and some other things. You can configure it so there is no bottom bar, or you can delete it completely (I think it's not what you really want).
If what you want is just to change the KDE loader (how it looks while it is being loaded), you can do so from KDE System Settings => Workspace Appearance => Splash Screen.
Maybe if you give more information about what your program is for and what you want it to do, I could help you better.