At what point do I get to include images in my signature?
Never. That is disabled for all ranks.
PS: I also could not figure out how to stop that "these many posts were done since you wrote that, you now gotta submit again" annoying message.
I don't think that is possible.
You can get rid of that actually. It's handy.
Profile / look and layout preferences / "Don't warn on new replies made while posting."