I'm pretty sure you need traffic for a domain to generate income. That means you either get people who mistype a domain name, the domain gets indexed by search engine, or you have it linked to from elsewhere. If none of this is true, I see absolutely no way for the domain to generate any sort of income, be it just parked or something more creative.
Typically, what people do to generate income off a random domain name is get it indexed by search engines. To do this, you need good understanding of how search engines work, and what sort of content they rate high. The most important bit is that with emergence of blogs, content does not have to be unique for a site to be considered a useful one. The important factors are how long the site has been around, whether it updates regularly, and how much content has accumulated on it. In other words, an automated blog does just fine. But there are a lot of nuances in making sure that people actually end up on your site when they search for something.