@Garfunkel: For sickbeard, couchpotato and the other ones there is no port, so this would be a bit different to create. I'm going to check that out, and i'll try to create theses aswell in the next days/weeks. I should be faster now, since I've build one working pbi now :)
I think the name "customplugin_1" comes from FreeNAS since FreeNAS creates the jail when installing the PBI and I've have not done anything to configure the jail creation.
For your nginx pbi, take a look at my post-install.sh in the scripts directory, for sabnzbd I had to install cheetah and some other things to get sabnzbd running.
@flz: The wiki says
Once you are satisfied with the PBI, update the PBI Requests page and create a forum post so that other FreeNAS® users can test the PBI. Once the PBI is well tested, it can be added to the PBI repository
but I don't know how to add it do the repository, first of all I'm gonna update the PBI Request page.
Oh and most importantly, I want to thank Joshua for his PBIs, they helped a lot and I re-used a lot of code from his work to get it done.