A couple of plugins have caught my eye, lately. One is a procedural landscape generator that looks smashing, although I have Worldbuilder, which is great for generating either geometry or height maps.
The results look good, although I am not sure how intuitive all the sliders are, compared to the amazing toolset in Worldbuilder 2. This is one I will watch.
The other is Human Generator, which I actually bought, with my own money. In a few clicks, Human Generator creates fully featured characters that you can customise, pose, emote and dress with just a few clicks. The results are good, although these people are best suited for stand-in roles.
It's actually great to be able to quickly feature characters. I hardly ever bother to provide a human scale reference, which is really useful when building spacey wacy stuff.