I have several suggestions:
1. An advertisement thread in the public Guild Forums. I'd make it artsy and descriptive with maybe a "What's Happenning Now" section briefly in the first post and a description or list of all the subforums in the guild. Also with a picture or two as well as a separate second post with a list of members and links to other sites.
2. More subforums with different topics. Here's a few suggestions were I running the guild:
Ghosts
Vampires
Werewolves
Roleplaying
TV Shows/Entertainment
Cryptozoology
Myths, Legends, Folklore
Superstitions
Witchcraft, Wicca, Magicks
UFOs, Extraterrestrials, Alien Encounters
An Art Subforum
Then of course the main forum could be renamed and feature the Welcome and Introduction Stickies. Other than that, it could be reserved primarily for Announcements, Guild Happenings, and Contests.
3. Contests. Ask for donations occassionally for good contests by setting up a guild mule for that sole purpose. Have best story contests, personal experience contests, Bump contests, Avatar themed contests, etc. Of course they don't have to be all at once, but every now and then they are fun.
4. Events: Mainly similar to the Gaia events like Halloween, Prom, Summer Festivals, Valentines Day. Granted we can't do actual Biting, Kissing, and Dancing things, but dates and times could be set for Balls (rping -based), Fishing Events or other events that people can participate in--for example, a time when people can meet up in Gaia Pinball, etc. Games in some of the subforums like trivia challenges for the TV/Entertainment subforum, or a "Name That Creature" game in the Cryptozoology subforum where you describe a creature and people guess what it is.
5. A re-vamping of the Roleplaying Subforum with storylines and people bringing in their characters so long as they stay within the parameters of the general overall storyline, but letting them add their creative differences of course.
6. Finally some pictures in the posts and better pictures on the Guild Homepage and even the Advertisement thread. This would also mean some banners and buttons too of course. A Banner contest might even be a good idea, never know.
That's a few of them for now. Lemme know what you think.