When you add your own photos for example the background, do you need to design your own size of the photo? or will Xcode adjust it when you put it in.
You should design the size!
Make 1x, 2X, and 3x versions
This is probably a dumb question, but since I need to size each photo myself is there a certain size each one should be?
This link is from Apples iOS Human Interface Guidelines and may assist.