A few changes I'd love to see...
To begin, GImageView is great :)
That being said, if the following changes could be made, then I'd really be happy with it.
Firstly, I would like it if, when you open an image directly with gimv, (eg. $ gimv /home/me/mypic.png) that you could also then access other images in /home/me/ by pressing page-up and page-down; right now you can only do this if you view /home/me/mypic.png by double clicking on it from inside GImageView.
Secondly, I would also like it if I could set the image-window to always start in full-screen mode. Please also consider making it so that the image automatically gets refreshed to go to the biggest size that fits (if that's your desired option) when you toggle to and from full-screen mode.
Thirdly, I would like it if you could make it an option that double-clicking on an image in "image-view-mode" toggles back to the directory+thumbnail view.
I would also like to know if you wouldn't consider making the splash-screen a configurable option (and not a compile-time option).
Lastly, I want to thank you for this excellent program. I use it all the time, and I really like it :)