In a demo I’m working on, I want players to be able to display 3D models (.fbx and .obj files) in the environment, allowing for others to view them. I don’t necessarily want the player(s) to be able to edit those models, but I wasn’t sure how to create a system to allow them to show them off to others. 

This really depends on the engine you are using.

But you will need to :

1. Host the models somewhere

1a. Suggestion: Convert the models on the server to a single specific format. Sort of like what YouTube does for videos. This will save you alot of time supporting this on clients.

2. Download the models from the internet (HTTP should be ideal for this)

3.Display them in your engine

4. Most important: Design some concept of discoverability: Assuming you have 5000 models on your server: How will players decide which model to view? For example: Do they need to take off their helmet? Do they need a controler? Etc...

4a. I have a feeling that step 4 is the most difficult one. Hosting & Downloading http is a synch, however navigating menus in/out of VR is hard.