[Plugin: SmoothGallery] Add a background image to smooth gallery

I’m currently using smooth gallery on my site and I’ve managed to customise it to fit in with my site… up to a point.

As I have an assortment of portrait and landscape photographs I’d ideally like to add a background image to the slideshow so that any space in the holder that the is not covered by the photograph has the same background.

At the moment I’m “cheating” by adding a background to each photograph in photoshop before uploading, but this adds extra work every time I want to update the gallery and somewhat takes away from the spontaneity of the next gen plugin.

So… has anyone got any ideas on how to add the background image instead of just using a background colour??

http://wordpress.org/extend/plugins/smoothgallery/