Can confirm LarterStyles is 100% correct. Workaround to change image in an existing deck is to restart the game. The first time the deck builder is opened it will work as intended to change the deck image. Subsequent openings of the deck builder cause a subtle but increasingly large/defined orange glow sprite around the deck image, which appears to be preventing the deck image from changing.
Can confirm LarterStyles is 100% correct. Workaround to change image in an existing deck is to restart the game. The first time the deck builder is opened it will work as intended to change the deck image. Subsequent openings of the deck builder cause a subtle but increasingly large/defined orange glow sprite around the deck image, which appears to be preventing the deck image from changing.