IncArts is a great youtuber who is involved in Graphics design for more than 2 years and his designs are one of the best i have ever seen.

Check him out, he has great Tutorials for Youtube Backgrounds and Manipulation stuff and they are very detailed and long, not very noobfriendly but not very hard either.( Speaks german)

If you don't speak german than just take a look at his Wallpapers, they are epic.

Hope i could help you or make your desktop background amazing.