I seem to have stumbled on another trend in book covers. I'm not a terribly visual person, so it takes a lot of repetition for me to notice things like this. My sister-in-law pointed out the trend in book covers of having disembodied shoes. I hadn't noticed, but then I saw them everywhere.
The current trend appears to be crystals. Particularly on covers of YA fantasy books.
See what I mean? I'm not denying that they are gorgeous covers, but those first two look almost identical!