well, in the first panel there's an overall texture that's like some kind of rusted metal but very softly blended, iT can be blended by screen layer mode or maybe overly, also there's a grunge texture on the uuper part, that's an easy texture to find, also there are some shapes that you can make by simple selection, and these shapes are just a bit clearer than the general background, and finally the sunlight is made by some clearer circles and a soft-edged brush around the sun of a yellowish color.
I hope that despite my english i have been able to explain myself properly, any questions or doubts about what i said feel free to ask
EDIT: i fixed some mistakes i had, now my english is a bit better, sorry for the mistakes i had but i was in a rush to write that so i couldn't check if it was right
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