This app was mentioned in 1 comment, with an average of 2.00 upvotes
I have no clue if it works on iphones, but I use MMA Midnight Scene. You can pick from 6 scenes (witch's house, dark castle, etc), and you can change the sky/moon, create particles, speed up or slow down the fog, change the height of the skyline, and change the color of the sky. I love it! I originally got it for my Evo (years ago). It has worked just fine on every phone since (the 2nd Evo, the S3, and now on my S5). I think I did a free trial and then paid a few bucks for the full app.
I looked it up and it looks like it is Android only. I am glad that you found something for your iphone though! https://play.google.com/store/apps/details?id=mma.wallpaper.midnight