Well.. lets hope this merges..
1. Can you download new backgrounds?
How do you mean? New backgrounds for the images or new backgrounds for the space behind the pictures in the program (essentially the artist's table if you will)
If you mean the image background, then you have to make those.
but if you mean the background in the program itself, then here's how:
*to do this you need to be in Fullscreen with Menubars mode, you can achieve this by pressing the F key*
1. Go to you color Palette and switch to grayscale sliders
2. choose a level of grey/black/white that you prefer
3. switch tools to the paintbucket tool
4. holding the Shift key and click outside the image in the background, you will replace the old color grey with your new color that you have chosen in the grayscale slider.
If you're using a Mac, simply change your desktop background.