I'm not a diehard collector, but I have a few:
Marina Sirtis (Troi, STNG)
Geri Ryan (7 of 9, Voyager)
Robert Picardo (The Doctor, Voyager)
Jennifer Lien (Kes, Voyager)
Ethan Phillips (Neelix, Voyager)
John DeLancie (Q, STNG...)
Robert Beltran (Chakotay, Voyager)
Tim Russ (Tuvok, Voyager)
Robert Duncan McNeill (Tom Paris, Voyager)
Shane Rimmer (American actor)
Richard Biggs (Dr Franklin, Babylon 5)
Claudia Christian (Ivanova, Babylon 5), signed Playboy Pic
Bruce Boxleitner & Michael O'Hare (Sheridan & Sinclair, Babylon 5)
Jerry Doyle (Garibaldi, Babylon 5)
Jason Carter (Marcus Cole, Babylon 5)
Bill Mummy (Lennier, Babylon 5)
Tom Baker (Dr Who)
Don S Davis (General Hammond, Stargate)
Eliza Dushku (Buffy, Tru Calling, Dollhouse)
Menina Fortunato (Orion Slave Girl, Enterprise) with and without makeup
Summer Glau (Farscape, Terminator and soon to be Dollhouse)
Jewel Staite (Farscape, Stargate Atlantis)
Nicola Bryant (Peri, Dr Who)
Fraser Hines (Jamie, Dr Who)
Ingrid Pitt (Hammer Horror faithful & Where Eagles Dare)
Dean Stockwell (Dr Yueh, Dune & Al, Quantum Leap)
David Carradine (Kung Fu, Kill Bill)
Michelle Dockery (The Hogfather)
Charisma Carpenter (Buffy, Angel)
Bobbi Sue Luther (Another Orion Slave Girl, Enterprise) with and without makeup
Patiricia Tallman (Lyta, Babylon 5)
Julie Caitlin Brown (Na'Toth, Babylon 5)
Mira Furlan (Delenn, Baylon 5)
Paul McGann (Dr Who)
Gates McFadden (Dr Crusher, STNG)
Grace Lee Whitney (Rand, Star Trek)
Kelly Hu (Lots of stuff)
Alice Krige (Best Borg Queen, STNG)
Jimmy Vee (Mox of Balhoon, Dr Who)
Juliet Landau (Druscilla, Buffy/Angel)
Yan and Rafael Feldman (Fanty and Mingo, Serenity)
Jonathan Woodward (Buffy, Firefly, NCIS....)
Neil Roberts (Season 1 of Charmed), still a nice guy, even with that
Michael Fairman (Adelei Niska, Firefly)
Christine Hendricks (Mrs Reynolds, Firefly)
Ron Glass (Shepard Book, Firefly)
Grace Park (Boomer, BSG)
Anthony Head (Giles, Buffy)
John Rhys Davies (Sallah, Indiana Jones)
Kenny Baker (R2-D2, Star Wars)
Anthony Daniels (C3-P0, Star Wars)
Ian Whyte (Predator), the guy in all the latex
Avery Brooks (Sisko, DS9)
Gemma Baker (UK Model)
Sophie Howard (UK Model)
Donna Marie (UK Porn Star)
Cathy Barry (UK Porn Star)
Rebekah Dee (UK Porn goddess)
Alexis May (Glaswegian Porn goddess)
Michelle Lay (American Porn Star)
Walter Koenig (Chekov, Star Trek)
Nathan Fillian (Mal Reynolds, Firefly)
Patrick Stewart (Gurney Halleck, Dune oh and Picard, Star Trek)
Helen Slater (Supergirl)
Tom Baker & Derek Jacobi (The Dr and The Master)
Tricia Helfer (Number 6, BSG)
Alexandra Bastedo (Sharron MacReady, The Champions), 60's show for those who haven't heard of her or it
Teryl Rothery (Dr Fraser, Stargate)
Eve Myles (Gwen Cooper, Torchwood)
Louise Jameson (Leela, Dr Who)
David Prowse (Darth Vader)
Shane Ragni (Lord of the Rings and a few others)
Peter Davison (Dr Who)
Ernie Hudson (Ghostbusters)
Paul Blake (Greedo, Star Wars)
Claudia Black (Vala Mal Doran, Stargate)
Nichola Brendon (Xander, Buffy), he was in the area, so got it
Christy Hemme (Female American Wrestler)
Doug Bradley (Pinhead, Hellraiser)
Gareth Thomas (Blake, Blakes 7)
William Hope (Lt Gorman, Aliens)
Gemma Atkinson (Actress, Sort of and Model)
Daniel Loyd (Model)
Catherine Bell (Actress most noteably in JAG)
Ray Wise (The Devil himself, Reaper)
Trevor Steven (Ex Footballer)
Dita Von Tease (American Burlesque Chick)
William Shatner (that man Kirk from Star Trek)
Amanda Tapping & Richard Dean Anderson (Carter & O'Neill, Stargate)
David Gemmell, Allan Dean Foster, Robert Salvatore (Authors)
With a couple still to get here.
A bit of a longer list than I expected, but it's nothing compared to the collections of the diehard collectors.