“Memorial” photo sets of the Inazuma Rock Festival performers will be available via Pia.
The Granrodeo set is 1,200 yen including tax and postage and includes 3 photo cards. It sounds like you can customize the cards with the date, venue and perhaps a few words to remember the show by.
You don’t have to attend the festival, but you do need a Pia account to get the sets. Sale starts on 9/21 and continues until 10/30. Cards will ship in early December.