How to change the image of external background when connected to projector? OS X El capitan 
version 10.11.6
Macbook pro 13-inch

Whenever I connect to projector, the projected screen has a old picture of me and it is quite embarrassing when I am presenting in front of professional crowd. I already removed that picture from the Desktop pictures folder but every time I connect projector, it still shows the same.
This is not happening when I connect to external display (monitor) though.How can i change this?
I suggest you plug into a projector and then use the Desktop &amp; Screen Saver Control Panel to change the background of the desktop being projected to something else. The new background should then stay the same anytime you plug a monitor/projector in.