Thank you for your reply!
I tested the code out and it looks good, because the images are indeed no longer flickering - so my biggest concern is gone.
However, currently when I press ‘a’, both images are shown at once. It may be because of my sloppy explanation, but it’s supposed to show one image at a time every time ‘a’ is pressed.
Also, my intentions were to bind a single key to spawn a new image every time that key was pressed. This would indeed mean that the new image would be drawn over the old image and that’s fine with me. But they don’t have to be turned off once they’re spawned. That’s way too fancy for my level of knowledge in Processing 