Thank you for your replies. This makes this engine even more advantageous to use.
The problem using the event queue is, that the runnable object is called after all pending events are processed, and this is causing flicker.
The solution I found is using the existing jpct buffered image, and by creating a new graphic object from the buffer, swing components can be drawn before displaying the contents. This lets me have swing components on the same pane as the rendered scene, but like it was a normal jpanel.
Best regards!