A few things... Kind of a brain-dump so consider if these things apply to you.

For people wanting to join your server if they start with your profile page:

1) You have no description on your profile, you're a blank wall. Some people would be put off by that. You can type the server name, game type and the IP address somewhere.

2) You don't seem to have a group page showing off that you have a server and why it should be joined. Might even be useful to know when you would be joining the server yourself.
You can put the steam page for this group as one of the three allowed hyperlinks at the bottom of your profile summary (and put your own profile page at the bottom of the group's summary)

3)Do you have a pro website related to the server? (special insignias, secret taunt-handshakes, etc) You can put that link on your group or profile page.

For people wanting to join your server from the server browser list and they already know you:

1) How do you name your server so it can be found easily?
Sometimes if I see a clan tag (usually at the beginning of the name) its a pretty safe bet (especially if there is more than one) that the servers are related and are being managed properly (assuming admins are actually there kicking spammers, etc). Additionally give the server appropriate tags so it can be found on a search. ("insta-respawn", "lowgrav", etc)

2) Can your server actually handle the physical demands of more than 8 people? on two teams? with perhaps using a mix of high and low speed internet connections? It might just be a hardware limitation which you can disprove by doing a stress test with 15 friends. (most respectable servers have a 32 player limit). I'm not sure if your server is your simple desktop machine or a multi-core rackmount beast in a datacenter you rent.

3) Does your server only offer stock maps? Make your own? Membership related free or paid benefits (like being immune to the team autobalancer)? Use some form of HLStats system for tracking how well your visitors are doing against eachother? Do you join them? If they have an issue can they steam chat you or email the generic admin? ("type !admin in chat to summon TheMasterer" etc.)

Do you add bots? That adds to the player count unless someone looks at minutes played and ping of each "player". But maybe they're truly evil, tweaked by yourself to be relentless and perhaps even intelligent.
I've been on lots of human vs bot servers and you can tripple the amount of player slots as long as bots somewhat equal humans. Training the bots to join one team is a neat trick, but training humans which team to join is something entirely different.

4) Does your server have an unskippable flash video commercial of extreme loudness on the message of the day page?

For people who don't know you or that you even have a server:
no idea
(I'm in this category)

You're not getting visitors except those who stumble upon it. Its a lack of clear advertising that your server is worth visiting(having only seen the name on a list and no other relevant info), particularly among the other well established populated servers.