When I was drawing Quicksilver I realized that I'm not really a big fan of most of his costumes. The old ones all feel too dated (diagonal zig zag and black underwear) and his newest costume doesn't quite look like the character to me. I took a lot of inspiration from his Age of Ultron look, but tried to make it more of a super hero costume instead of athletic wear. I also liked the idea of him having stubble since there aren't too many characters that can get away with it.
I honestly didn't expect to like Wanda or Pietro very much in Age of Ultron, but boy was I wrong. They were both such great additions and Wanda especially was a scene stealer. I went with more of her modern look, even taking some influence by some proposed movie designs, and of course had to include that head piece. Is there a name for that thing? It's definitely not a mask. Anyway, I wanted to avoid the pink body suit and red corset combo, so I went with the newer jacket look.