I don’t think anyone can host a relay right now aside from bluesky.
People can host their own data / Personal Data Server, which is somewhere between self-hosting a mastodon instance and creating an account on someone else’s instance. The actual equivalent would be self-hosting your masto account separately from any instance (which is just not a thing with the current state of mastodon nor activity pub).
I don’t expect ai/LLM tools to make it easier to create nice looking art, but they should make it easier for anyone to create their own placeholder graphics that at least would allow them to run the game on their own.