still dont know how to define the pictures and how to command them.
Hold up your Arduino. Do you see a place on it to display a picture? I didn't think so.
What you CAN do is send a message to the PC telling it to display a picture. Send the appropriate message when a switch is pressed. Send another when the switch is released.
Then, write an application on the PC that reads those messages, and displays the appropriate picture on the PC screen.