I have listed some high quality assets that you can use when making interior scenes. I use some of them myself. They are ready to use for archviz purposes.
- Fabric Materials - 56 Pack
- Advenced Glass Shader
- Advenced Glass Material Pack - Free
- Wood Pack 4K
- Wood Flooring Vol.01 - Free
- Wood Flooring Vol.02 - Free
- IES Light Profile - Free
These can be used in interior design, but they are little bit advanced and specific stuff.
And of course there’s a whole category for architectural visualization. Here you can find what you want:
ARCHITECTURAL VISUALIZATION
As far as I know Unreal Engine 4 can be used freely for educational purposes and assets can be given to team members / students etc. You can read the end user agreement to be sure. Also Marketplace F.A.Q.