The other picture that POTUS is facing, which is shown in other pictures from that day, is a phone of himself aboard Air Force One flying to Philadelphia on January 26, 2017 speaking on his iPhone 8+ (may conceivable be a 6+, but it is large and has a home button).
He appears to be holding the same white iPhone with gold trim while seated in Scavino's office that day.
https://www.politico.com/story/2018/05/21/trump-phone-security-risk-hackers-601903
Scavino's screen saver is a run of the mill Mojave Desert screen saver image. It's a reversed (dark/light) image of a more standard picture. Windows operating system most likely.
https://focusrite.com/en/news/were-supported-macos-mojave
https://www.cnet.com/how-to/get-macos-mojaves-awesome-dynamic-desktop-wallpaper-without-mojave/