Batman is one of the big three as far as DCU is concerned and arguably one of the most popular Superheros ever. This shield is inspired by the Dark Knight films with Christian Bale.
John Stewart was an architect who was selected by the Guardians of the Universe as Hal Jordan's backup after Guy Gardner was seriously injured in a disaster. Although Jordan objected after seeing that Stewart had a belligerent attitude to authority figures, the Guardians stood by their selection. Jordan complied and recruited and equipped Stewart with the standard uniform and power ring.
This shield honours one of the more interesting Lanterns.
Guy Gardner is the third Green Lantern of Earth, and a member of the Green Lantern Corps assigned to Earth, known for his brash attitude and machismo.
The jedi were protectors of peace and Justice for over a 1000 years in the old Republic, before the dark times, before the Empire. During the fall of the Republic in the Clone Wars a shield such as this may well have come in handy for fighting those pesky Droidekas.
Alright alright I get it!! Superman doesn't actually need a shield cos hes pretty friggen invulnerable anyway, but... you are missing the point. The symbol is the crest of his family (El) and it stands for Hope. So why would they not have a shield with the old family crest on it to put about the fireplace or nuclear furnace?
OK so some of you are probably saying "But Superman doesn't need a shield. granted, but the question should be, do you? Consider this as an expression of art depicting the crest of ancient Kryptonian "House of El" I mean come on if they can have Crests and whatnot for Game of Thrones, I can create some for the DCU cant I?