I also have the parameters set to close the window with the "Esc" key ...
ESC key always closes fullscreen window. It does not exist any parameter to do this. Maybe you say "exitkey" parameter? This parameter only works in standalone player and it closes the player with ESC key.
I added a new parameter "closeimage" to set the image showed for this button. You can define one image for the button (JPG or BMP):
or two images (separated by ','), for "normal" and "over" states of the button:
Black color of the images is trasparent color.