When creating a theme or using an image, the image has a wide black strip down each side. Is it possible to change the black to white or resize the display to the image size?
Not currently no. You will need to resize your image using your favourite image editing software instead.
Have you try to change your projector's screen resolution to something like 1024 x 768 or even lower? I have tried on my second monitor (or projector) and it doesn't give me that blocks on the left and right anymore... Hope it helps. Praise Him. . .