This presents a problem for many artists because filing copyright registration can get expensive. Focus on designing for your favorite companies. This is a standard thing in the industry. They offered a decent typical market royalty to artists for every print sold and even later, a small percentage on their framing, which they do in-house.
Other Artists Look for artists with a similar target market to your art. Determine how you will establish and maintain ownership over what you create.
A fashion designer? So that way is a bit of a gamble.