I'm assuming the costume you're referring to is the Elven Hero Costume. That has come back a couple of times. Once in crates, I believe, and then it returned to the store at the launch of Summerset. Don't know if it will come back again, though, but it could.

Check out the monthly Crown Store Showcase (in the news section of the site) for a preview of items coming the following month. Hopefully, there will be things on the horizon that you would like to purchase.

Also, they keep removing items from the Crown Store, which makes it even more difficult for players to find something they want. A lot of that stuff returns in crates, but not everyone wants to gamble for them. I wish ZOS would have a broader selection of items available all the time. But, the limited-time model seems to work for them. I know that I generally only buy things if I REALLY WANT THEM NOW, like all the Dunmer outfits. Other items that I want, I usually only buy them if they're limited-time or if they're being removed from the store. Or on a decent sale - they do periodically put items on unannounced sales.