Hi Peter, you can bind different textures to different surfaces - any number of them using glBind. but multi-texturing is using more than one texture onto a surface at the same time, which is not a subject I am familiar with. NEHE lesson 22 is probably the most helpful resource for this, though it gets very technical. It involves using Opengl extensions.
The perspective on your cube looks as though you are using orthographic projection, giving the illusion that the cube is distorted since more distant parts do not reduce in size.
Charles