A while ago I submitted a 4K gallery with a link to my imgur folder containing nearly 200 4K in game screens.
This folder has now ballooned to over 700 screens! and I invite you to have a look : https://imgur.com/a/ObKcU
Please feel free to download and use any of them, Please upvote if you like my submission.
Here are the links to my threads in both General : https://robertsspaceindustries.com/spectrum/community/SC/forum/3/thread/4k-screens
and Subscribers den : https://robertsspaceindustries.com/spectrum/community/SC/forum/6/thread/4k-screenshot-thread
And below are some examples, Enjoy.
Thanks for viewing.