
Yes, that big black section in the middle of the screen is a black hole.
To create this, set the planet texture to be a PNG file with nothing in it (that is, not all white, or all black, but delete everything). Set the planet texture to that. Then set the illumination color to [0, 0, 0] and you get something like the above screenshot. You'd probably need to set a few other things in planetinfo.plist (cloud settings, I'm thinking, making sure there aren't any, atmosphere settings, etc). But from a visual point of view, it's a black hole. Not a black sphere that has reflections. But, for all intents and purposes, a black hole.
*Big caveat*. This only works at a graphical level of "Shaders Enabled" or "Extra Detail". Anything below that and you see something like this:

Edit to add: you can see some of the reflection on the moons surface in the lower half of the shot.
Here's a demo OXP I put together for this. BlackHoleDemo.oxz. This will add a "Black Hole" a *really* long way out in every system. Please note: there is no gameplay in this demo (ie gravitational changes, proximity dangers, time skewing etc). It's just a tech demo. If someone wants to play around a bit more, they are welcome to grab with demo and run with it.
Anyway, I thought it might be worth sharing to get those creative juices flowing!
Note: You might want Galactic Almanac installed, as it will put a beacon on the black hole to make navigating to it reasonably easily.