Why orhtographic lens when Perspective can give you the the square image just a well?
I choose to use Orthographic because helps "flatten out" the view of my decal, so that I'm not getting weird perspective in my final render. This decal may not be the best example for the difference between the two, but depending on the surface rotation of some of your decals faces, it can give you unintended results for your normal map values, such as normal faces not pointing in the correct direction or casting at different directions even though a face may be completely straight on your model. That being said, Perspective view is totally fine! All depends on whether you are satisfied with the final result or not. :)
That makes sense. You might want to put a note in the presentation about that... good thing for us beginners to know..
thanks again
chuck