When sourcing velvet prom dresses, the fabric composition is the most critical factor. For premium markets, prioritize silk-base velvet or high-grade rayon blends which offer a superior drape and luster. For the mass market, high-density polyester velvet is more cost-effective and durable. Ensure the fabric has a weight of at least 250-300 GSM to prevent transparency and ensure a luxurious feel. Additionally, check for 'pile recovery'—the fabric should not leave permanent finger marks or creases after being pressed.