It would be quite natural to assume that a spirit being so grossly evil would also look evil. The popular perceptions of Satan are usually either that of a sinister-looking individual in all-black clothing, or a comic character in a red suit with horns and a pitchfork, but The Bible, as in the above Scriptures, describe Satan with "beauty" and "splendor." Satan appears righteous:
There is much written in the Bible about Satan's change of behavior, but nothing about any change in appearance. He is the ultimate evil, and yet he appears attractive and righteous. The references to him as a "snake" or "serpent" refer more to his sneaking, slithering, underhanded personality than his actual visual appearance.
Along with the fact that the rugged and ordinary-looking Jesus Christ (Isaiah 53:2-5, see also What Did Jesus Look Like?) looked almost nothing like the pale "pretty boy" who is so often portrayed in Christian art, one of the most startling questions of recent times involves just who it is that's actually portrayed in those images. What very powerful deceiver, and, as the Bible describes him, impersonator, could have easily influenced all of those various artists, over the many centuries, to depict someone who's consistently the same in un-Christ-like appearance?
Fact Finder: How did Satan originate?
See Did God Create The Devil?