yes u can delete after you are done.
and i think u have to rename the files 01 02 03 for each month but if u want the same backround for each month just put 12 files named 01 02 03 etc up to 12
try reading the readme
i recomend a program called X-flash rather than theme psp alothow it is a good program xflash varifys flash writing reducing the chance of a brick
plus that link is dead but i think all backrounds on psphacks are checked and xflash would alos check the size
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