Doing slideshow texture projection was really very trivial. All I did was discard the z component and map x and y into u and v. The only instance I can think of using this method (other than for maybe effects) is where the viewer will never see the side perpendicular to the projection, i.e. a plane, or some other surface (maybe a planar overlay).

Slideshow projection on the face of a cube. One normal per face.

The slideshow projection is now tiled across the face. Here we can see the streaking of the texture on the faces perpendicular to the texture. On the top face and top side of the near face, aliasing of the texture can be detected.

We now apply the slide show to our good friend the tetrahedron. Interpolated normals per face.

Look how it tiles! Cleans the windows but leaves streaks! New and improved slideshow tiling. Or maybe not so improved.