The only way to delete the data is to go into your device Files > the game's/version's file > "game" folder > "saves" folder, and figure out which save is which.
The best way to do this is to save the desired saves into the first, second, and third slots (as needed), on the first manual save, and avoid deleting "1-1-LT1.save", "1-2-LT1.save", and "1-3-LT1.save", as they're the most obvious.
As far as the pictures of the saves go, I don't think there's a way to clear those, unless I'm just mistaken, and it's possible.
Alternatively, you could save-flood, and replace all of the old saves with new saves, by going over them.