Here's how to change right-column banner images.
1) Create an image that is 140px wide
2) Name the image "banner-<short name of its top-level section>.jpg", for example:
banner-wind.jpg
banner-solar.jpg
banner-biogeo.jpg
3) Upload this image to images/banners
Note that you can only specify custom banners for top-level folders, and they will then cascade down through all of that section's subfolders.

