At this point, we all know that Scarlet Witch is going to be played by Elizabeth Olsen [remember the cute lil' baby girl called Michelle from the sitcom Full House? Well, Elizabeth is the younger sister of the twins Mary-Kate and Ashley Olsen, who both played that little girl like matching stunt doubles].
And Quicksilver will be played by Aaron Taylor-Johnson [he was the lead actor in the rather controversial Kickass movies]. Anyway, I added the blur effect to the pic of Quicksilver below just to make it look cooler, since he's Marvel's version of Flash.
Take a close look at these movie costumes above, and compare them in your mind; and see if they really give you the right vibe. Personally I'm wondering if they are only going to be the "temp-gear" worn by Scarlet Witch and Quicksilver [while they are portrayed on-screen as new recruits], v.s. their final team-member costumes, kinda like what Captain America and Black Widow usually have on.
Beyond the crooked-left-leg pose that Scarlet Witch was displaying, I was also a bit concerned about the on-screen chemistry that the director for Marvel's Avengers 2: Age of Ultron is going to create for these two new recruits. Remember that they are a brother & sister team; and that means the director Joss Whedon has a chance to make them a bad-ass fighting duo, or a creepy lip-locking couple [as is portrayed in one of the past Ultimate Avengers comic storylines].
Nevertheless, I hope to see more real costumes for the two new characters, since the attire that they have on in these behind the scenes photos look more like street clothes, as opposed to sleek combat gear.