As I was about to delete one of the photos I suddenly recalled a website I once stumbled upon - "Stereo Images - Time for Space Wiggle" (probably not safe for work - the site contains nudity) - which demonstrates how you can get a 3D effect by "wiggling" two images of the same subject, taken at slightly different angles...
So, without further ado, I give you Carnotaurus Sastrei:
I'm no GIMP guru, but it wasn't too difficult to create this:
- open the first image in GIMP
- open the second image as a new layer (File->Open As Layers)
- scale the image to a reasonable size
- save as a GIF image, and when asked select the following: save layers as animation, loop forever, 10 milliseconds delay between frames