Here are some background pictures of several candidates.
I think first image look good
When I tried to add as Wikibackground but it's say "Incorrect file size".
You need to make the image smaller
It look real in life, we can't use real life as wiki-background.
Btw, the image size can't larger than 300kb.
At the same time, the image aspect ratio should be considerated as well (for example, 1360x600, my laptop)
What do you think?