I and my team is ready to produce a FREE content, for all directions, like 3D models, music, special texture and etc…
But how quickly our content will be appearing in UE Marketplace depends not on us 
For example, I have ready 2000+ 2D sprites, i designed for the adventure game genre. Time spent to work, about 1000 hours.
It’s houses, plants, trees, many props, rocks, clouds and sprite sheets animations, lightning, fire, birds and etc…
And i would gladly shared it with the community, absolutely free, i want so that people are more focused on creating a unique and exciting gameplay.
Small team, one developer, big teams, all We Are a Community, - it’s like the blood vessels to the body, and if the blood ceases to circulate…
We must never cease to circulate.
Best Regards.