Official registry of lunar placenames? What's the definitive source for names of geographic objects on the moon?

Reason: As a computer graphics project I've rendered a scene based on LROC terrain data. I want to know what I'm looking at.

The most detailed atlas I can find online is this one:

http://planetarynames.wr.usgs.gov/Page/Moon1to1MAtlas

...but it's not brilliant and there are lots of small but prominent craters and ridges which aren't labelled. It may be the some of these simply don't have names, but it's also plausible that there are simply too many to list in that atlas. How can I find out for sure?
The resource you cite, in addition to this full list of crater's names are the official, definitive lists of named craters. Note that you have the coordinates of each crater in the complete list; I guess you could reuse these informations for your project. As for the atlas, it is specified in the "introduction" of the atlas that the list is up-to-date with the approved nomenclature of lunar craters.

The IAU (the International Astronomical Union) is the official organisation in charge of naming celestrial objects et al. You can rely on it.