I am a concert photographer and often sell my prints online with the Paypal function button. One option I propose for exploration would be the inclusion of an Adaptive Payment function which allows the seller to be the "middle man" in essence. By doing so they can pass a percentage or flat amount of the sale on the model or band for each sale.
This currently exists in the business developer portion of Paypal and is termed an "adaptive payment" however due to limited knowledge of code and such and API keys etc...I am unable to add this function to my existing paypal buttons on my site.
I believe this could open a large untapped niche market for those selling products which could have the opportunity for a two way payment to support the contributing artist and model.
I look forward to your response, time and consideration of this idea.