This was just something cool I wanted to do, a head canon for how shields in Mother 3 would look. The reason the shield is an outline is because in the game it says the shield "envelopes" the characters. As such I think it would fit somewhat snuggly like so. The reason for the pattern is that when you use the shield, there's this effect that's kind of rectangular. I imagine the surface of the shield would look something like that.