Nice idea! How about the geo fields (LAT/LON) which also have a great impact on how the sun renders... ?

That would be possible.

Extra info such as the render camera settings would definitely be useful.

I did consider embedding the geo data, but I wasn't sure I wanted GPS coordinates to my house buried inside the images, especially if it was a overhead plan view (I'm sure you're all nice people, but...). If this were to be done, I think it would have to be controlled by a setting that would default to off.

If the eTeks decide to fold this code in, I don't mind putting it some effort to include a few more attributes.

Initially I wasn't sure whether displaying text on the image was totally necessary. But metadata embedded in PNG's is only supported by a few imaging tools. It turns out there is no well established metadata standard for PNG's (that came as a bit of a shock). That pushed me to experimenting with an option for annotating the actual image.