I would get a better website design. Nothing too professional, just not as amateur as it is now. When a website is too amateur looking, people are more hesitant to use their credit card. A better design will improve your signups from the traffic you're already getting.
Here is an example of some amateur sites that have decent design:
www.creamypies.com
www.jeanswing.com
www.wantonwives.net
I would also raise your price to $24.95/month, I seriously doubt you will see any dropoff in signups.
Other than that, you should be making small free sites to submit to link lists, TGP galleries, and AVS