Well, upload content through Adobe Stock (create an account), and if it is approved it will be available to 1000s of customers. And you will get paid for your content.
It’s not foreseen that people voluteer for free images. You get paid, even if someone buys your picture with his 10 free images or during his first free month.
From time to time, Adobe licenses pictures from Behance for the splash screens of their applications and may be also for other opportunities. But that is Adobe coming forward and contacting you on your content.