Hi, truthfully...I'm not sure. I'm not running 8 yet on my iPhone 5. When I install a theme I get the icons but that's about all. I have to add a home screen background & lockscreen after the fact separately. I wish I could help you more... but that's all I've got. have a happy Turkey day :)

Will this work on ios 8.1 iphone 5s?

On my 4s the Mail, Cydia, and Camera icons do not change. They are the Apple icons. Why?