Craft an extraordinary retro 90's poster featuring a photorealistic depiction of the BMW E21. Embrace the aesthetics of the era, blending it with the timeless appeal of the E21's design. Create a photorealistic illustration of the car, capturing its sleek lines, distinctive features, and retro charm. Utilize a color palette reminiscent of the 90s, incorporating bold and vibrant hues that evoke nostalgia. Employ typography inspired by the era, with bold, geometric letterforms that exude energy. Consider adding iconic 90s elements such as neon lights, geometric patterns, or even cassette tapes to enhance the nostalgic atmosphere. Experiment with lighting effects to make the car shine, casting dramatic shadows and highlights that accentuate its photorealistic qualities. Achieve a composition that balances the prominence of the car while incorporating visually engaging background elements, transporting viewers back to the vibrant 90s.