Well I tried making 5 framebuffer tiles the same dimensions as my screen resolution and drew all of them as a test (disabling my normal parallax bg first). I got a much lower framerate than when I had my regular parallax! I guess I've optimized as much as I can.

Programming a game can take a tremendous amount of time and effort. Even more so for a multiplayer game, and more so than that for an MMO-style one. Ideas are useful, but implementing an idea is the hard part by far, plus for an MMO you need a lot of money. I'll give the same advice (19:25) given by...

I don't think I want framebuffers that big.

Gah, spritebatches don't let you set the color of stuff you add to them. Lame. :/

How would I go about making the stars loop back to create an 'infinite starfield' using those methods?

I looked into those, but I'm not sure how to implement them so that they'll work with my stars which move at varying speeds and "wrap around" the screen.

I have a parallax star background in my game, but drawing it takes a significant chunk of resources (I get 55% more FPS when I don't draw it). Is there a more efficient way to do this, or some way to better optimize my code? I made it have random depths (and sizes) because I think it looks a lot nic...

Adding to the list of ideas, a multiplayer tank game sort of like a 2D version of BZFlag might be cool.

Why all the MMO suggestions? For a persistent world wouldn't we need to host our own servers? / sounds fun, I'll do it! :D I like space games the best, but that's just me. I know at least a few people who would love something similar to a multiplayer EV:N. I might be able to get my friend to make so...

Depends what your goal is.

EV: Nova is one of my favourite games. <.< >.>

I eventually want to see if I can do some sort of multiplayer for mine, but I might not get that far.