What I did was take an existing these from here that I liked and edited it in the theme editor, you have to go through the settings to figure out which is which and change the colors. The user defined are customized entries, if you dont want to use those you can hide them and create your own. The wallpaper was made in photoshop and added to "UI Image". After i was done I saved it and it saved to the 35inchENG>Config folder. Close the app and restart to see your theme in the drop down list.
The only thing I couldnt figure out was the status bar settings, there are 2 versions, the one that appears to be loading and the back layer, I can move the archstatus but I cant move the back layer, so I kept them in the same position and created the format around them. Hope this helped.
The theme I made was for Kpop group ILLIT's Super Real Me album theme.
Example
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