This: >>/37724/
Bernd and related knows this place already, but they opt not to post here. You could catch new users if you are willing to seek out the disgruntled on Kohl, but they are often want an alternative which pace is similarly quick as Kohl's.
What could we do?
Keep together current userbase. Replying to newish users, and those who just pop in once in a while, keeping them engaged shows them it's worth to stick around, their addition to the conversation doesn't go unnoticed. You are lucky you have common topic with Danebernd, since we are few our interests might not overlap, and we lack redundancy to spin multi-person discussions frequently.
Fishing for individual users on other IBs. As I stated above it's complicated.
Help Endchan to grow. As Polan above said as new boards open up, new communities move here, some of those users will look around and post on other boards. We could make people be aware of the existance of Endchan and offer them a place to post, then help their acclimatization, and raise awareness of the world surrounds them. This need to be done unobtrusively, otherwise it would just alienate the potential userbase, and they won't move here. So spamming the chan everywhere is out of question.
In addition of the previous point we have to keep Endchan online, and away from such dramas that knocked out 8chan. It should be a safe harbour for anons all over. There are lots of small (tiny) altchans but they are kinda fragile, and I read some even exploited the users by harvesting and selling their data. We have to be stable as much as possible, and clean, trustable - well as far as trust can go on imageboards.
Now that we are talking about altchans. Those guys - as Ernst and Kohl - are aware of the existence of Endchan. The only big pond around is... 4chan. /bbg/ was formed from those guys, just like /ligamx/ And actually it's a fair chance all of us started their IB career there. I'm not talking about flooding End with newfags however.