I retired my banner that I put together in my hospital bed in 2004 and have set up a set of new banners that get picked randomly with page requests. The original aspect ratio was just too long at 8.84:1, so I shifted it to 8.84:2.
GIMP provides a selection tool for a fixed aspect ratio, which was just what I needed. Rotate, crop, scale, apply levels, unsharp mask, and I can save off another banner image. I’ll try to add more to the mix as time goes by.