Hey. Turns out there was a pretty large error in my code in my Sprites module! :S
The bug prevented planes from displaying the image under certain circumstances - this should fix that error. Since it's such a simple and small fix, I'm just providing the Sprites.py file for download.
Python Script File - MediaFire
Python Script Link - PasteAll
So, either download the script file from MediaFire and replace the one you have present in your game directory / Blender directory, or copy the script from PasteAll and paste over the code in the Sprites.py file in your directory with the copied code.