Browse to the following location on your hard drive:
C:/Program Files/BioExplorere/Flashbg

There you will see 4 folders. Each folder represents one of the image themes in roller ball.
To install your own folders you will need to replace one or several of the current .jpg files with your own pictures. It is recommended that you backup any files that you replace so you can restore them later if necessary.

Example:
Remove photo6.jpg
Replace with your own .jpg photo and rename the file photo6.jpg

If the images look funny, sometimes cropping it or resizing it to be 800x600 will help. I recommend a free tool called irfanview www.irfanview.com to easily crop and resize images.