Turning 4 bytes into 256 bytes

Objective How we can we leverage pseudo random number generators to our benefit. Setup Perhaps you want to generate one of these lovely tiles Or generate the following string bAjFcOcLbMnBfKaHgIeNmGcDpEaJhChPmAaFfObLmMeBiKpHbIlNpGbDkEhJkCgPhAhFiOaLh...