Hey There,
**To change the header styles you need to select the transparent header style first.
goto
wp-admin -> Appearance -> Customize -> Header -> Header style -> transparent.
Now you'll get an option in the courses to choose the title background image, so you can add different background images for different courses.
1) Goto
wp-admin-> lms -> all courses -> edit course > title background image > set the image.
Refer:
https://prnt.sc/k1jith
2)Please goto
wp-admin-> wplms-> header-> upload title background image, and it will change default title background image on your all pages.
Refer:
http://prntscr.com/ldfa9c
hope this helps