Here's a thought I've had regarding promoting new groups of art work. Create an email (or snail mail) list of "Insiders" who have bought your work in the past and/or people who are really serious about buying it. Don't put everyone on the list, just those people who really should be on it. Put everyone else on a "general" list.
When you have a new group of artwork, send the "Insiders" a notice. Tell them that you're thanking them for their past support and that you're offering your new works to them first for a limited period of time. Your "Insiders" will feel good because they are getting preferential treatment and first opportunity to see your work. This has the added bonus of creating a bit of time urgency for them to act.
One of the web services that I have created includes a "Membership Manager" and you can assign "Insiders" a higher security level on your website than "general" members. You could create a page of art that required members to log in to see the art works. This has an added benefit. After they log in you will know exactly WHO is looking at which pieces. (Although I've created this capability, I don't know of any artist who has used it in this fashion to date. I suspect I would need to assist with setting this feature up because it would require being tricky with filtering which works were shown on certain pages.)
Another option would be to simply leave those pieces off of your website until the insider group had seen them by email. Or to create a web page that was not linked to. (IE only found via the email that you send them).
After the insiders grace period expires, you could simply remove the security on the page and make it available to the general public.
Software Craftsman and Art Fanatic