I haven't found another place to post suggestions, so I'll just post the ones I have here. It will probably be updated and grow over time, hence the 'list' part.
1) More advertisement. Bioware social network, NWN2 Vault, etc. I think this has been done, but there are many more places to advertise the PW and it may increase population. I know all the servers that were small that I played on, I found through advertisement. I didn't quite locate this one anywhere on the net. I just sorta found it listed in GS.
2) Update the rules list. Not to change the content, but the wording of the rules. In my opinion the way in which the rules section is worded makes it sound a little draconian and may deter new players. At least that was what someone I know mentioned, so it may be worthwhile to reword.
A neutral, yet serious stand-point would be something to consider. Instead of "You will not, under any circumstances..." you could opt for "Players cannot, under any circumstances..." etc.
3) Something to consider as you approach the end of play-testing is a few scheduled and announced big events. I've helped build up three of the more prominent NWN2 servers and DM'ed on them, which allowed me to see what exactly helps encourage population growth. This is one of the things that puts the little guys on the map officially. It will bump the player count for a while and push it up further on the list. The longer it stays up there, the more likely people are to notice it and check out the site.
4) Player RP searching and detering tools. A 'search for others' token that you can choose not to appear listed on (pros and cons with this) and/or a black list on the player list. Too many times rogues and other sneaks have been thwarted by metagaming because people open up the player list and see one or more "Friendly" people in the zone with them. I suggest that these two be considered only after player population picks up, however.