Is posting a link to Liveleak allowed here?

That's fine. Just be sure to post NSFW in the the thread title and be pretty clear up front in your post that it's going to be graphic. Also, I would generally recommend there being a point to the thread. If it's just to post lots of graphic gore, that would be in poor taste and probably not okay. Some people's kids do browse the site, so it would be best if we have a bit of restraint and not go off the deep end. If it's, for example, to catalog video evidence of defensive shootings for further study, or to use as a demonstration with video for a particular aspect about crimes, self defense, etc. that's fine.