Here are the rules for alt art naming:
Option 1: The name is the same as the card ID with one or two letters at the end and the / and - replaced with _. Any E in the name before the number (signifying English edition) is ignored.
Option 2: The name is the same as the numerical part of the card id, preceded by T for trial deck or P for promo, with 1 or 2 letters at the end.
There can only be 1 or 2 letters at the end, not 3, so OFR and SSP rarities need to be renamed.
Only the last letter is actually used when there are 2, so you can't have one named 001aa and another named 001ba.
Images must be png or jpg