You're probably here b/c you want to add grade-specific backgrounds for the theme.

DO NOT DELETE
"Grade_Cleared" or 
"Grade_Failed" folders

(you may remove the placeholder background images inside if you wish.)

Images in "Grade_Failed" will be loaded for failing scores,
Images in "Grade_Cleared" will be loaded for all passing scores.

In addition, to add backgrounds that are grade-specific, (e.g. only shows upon AAA)
create additional folders with the SM's grade tier as the title. (Grade_Tier01 or AAAA has already been done for you as an example)

The theme will then load the backgrounds from the "Grade_Cleared" and the "Grade_Tierxx" folder.
(If the grade specific folder is empty, the theme will revert back to grade_cleared folder for background images.)