If we have this feature now, let's use it and give the wallpaper authors the credit they deserve rather than being tucked away in the tooltip.
Good idea +1. I think an author's name is enough here since information is displayed in a similar way that songs info is ie. it should be obvious to everyone the second line lists the author.
"By" can also be tricky to translate into other languages. In my language you can't just literally translate it because it would mean the wallpaper is made of the author's flesh. So instead of that the translator would have to add "Author: " everywhere or just omit it.