I have about 1000 people who are part of my newsletter. It took about 9 months of promotion to do it. These people WANT to know what I have to say cause they asked me for it, therefore they are not offended with my art promotions and sales. Get a referral program started. This simple cgi program allows a visitor to recommend your site or page to several friends via e-mail.
Nothing brings in traffic than a good referral.
Start a contest. Raffle a print or a service. Set up a simple form and post the rules and the deadline. Add if they want to join your free newsletter while they're at it. Offer everyone who wasn't the winner a discount on something in your gallery.