I've put links to two zip files using your morph.blend as a starting point with various combinations of material/texture transitions from one state to another using Blender Internal renderer. If any of them are close to what you are wanting to do then that will give us a better starting point. If I'm still way off the mark then PM me and I will give you an email address to send me your blend file to look at.

Forum: Blender

Subject: Texture Transitioning problem.