While girls in pretty dresses are still ubiquitous on YA fantasy covers, I've noticed more and more are featuring objects much more prominently, particularly in high fantasy (as opposed to paranormal or other subgenres). It's a refreshing change for someone like me. I remember many books I read as a teen featuring the (usually) magical objects within the stories, leaving the look of the main character up to my imagination.
I admit that I may just be seeing an increase in these types of covers because high fantasy itself seems to be making a comeback in YA, but the covers are beautiful. They work really well for high fantasy, since they enhance the world-building so vital in stories like these.
(I also think it's interesting to note that two of the biggest YA book series right now, Hunger Games and Divergent, both feature objects, rather than people, on the covers.)
Sometimes, the object is a sword or knife:
Sometimes it's a crown:
Sometimes it's a jewel:
Sometimes it's a key or set of keys:
Are there any others you find particularly striking that I've missed?