Love or hate the figures, the concept is good.
The problem is, it can be a bit too random.
So my suggestion would be to have a second surprise figure series thats more focused, and could be released once or twice in a year, shortly before a mayor theme is launched.
This year will see the return of Western after many years for example, that could be accompanied by a release of male and female western figures that are not seperated by gender.
All figures of this series would be compatible with the western sets and could give better results when mixing them up instead of mostly silly combinations.
Heres a few lists of suggestions for various themes their figures:
Western.
Various cowboys, cowgirl, bandit, Undertaker, Confederate soldier, Union soldier, Indians from various tribes, Banker, Dancer, Barkeep, Blacksmith, goldseeker, Rodeo clown, Country singer, Mexican cowboy, gentleman, lady, con artist, sherrif, old lady, Pastor, Stable boy, drunk, gambler,
Medieval.
Blacksmith, Herald, Bard, Farmer, maid, stable boy, Gypsy fortune teller, Gypsy dancer, Gypsy musician, Teutonic Knight (with horned helmet), Highlander, Princess, Noblewoman, Nobleman, Musician, Tavern Wench, Guardsman, Sailor, Sculpter, Painter, Elderly advisor, Bischop, King, Queen, Prince, Hospitaller doctor, Merchant, Woodsman, Monk, Viking, Norman Knight, Mercenary, Janissary, Mongol Archer, Arab spearman, Beggar, Spy, Diplomat, Prisoner, Tax collector, Squire, Hunter, Renaissance doctor, Berber, Irish warrior, Templar knight, Harem Dancer, female knight, Milkmaid.
Modern.
Policeman, Female swat agent, Firewoman, Doctor, Nurse, Judge, Cameraman, Reporter, Maid, Handy man, Guitar player, Singer, Dancer, Astronaut, Tennis player, Golfer, Diver, Asian tourist, Train conductor, Actress (with oscar in hand), Bodyguard, Thief, Sailor, Construction worker, Salesman, Office worker (in a suit with laptop), Waitress, Juggler, female clown, Mail man, Bride, Priest, Clicky in gorrila suit, Old woman, old man, coast guard.
Pirates.
Musketeer (old french style like the three musketeers), female pirate captain, sailor, Redcoat grenadier, Scottish bagpipe player, Dutch blue guard soldier, Napoleon, very unfortunate pirate (eyepatch, wooden leg and hook), black female pirate, Prussian Grenadier, Arab pirate, noble lady, nobleman, fat merchant, carpenter, Dockworker, Duelist, Spy, Conquistador, Blackbeard, gentleman pirate, Navigator, officer, peasant lady, shipwrecked soldier, Italian sailor.
Ancient.
Praetorian, old philosopher, Spartan Hoplite, generic hoplite, Egyptian civilian, Greek/roman noble lady, Celtic warrior, Persian warrior, Roman spy, Centurion, Legionaire, barbarian male civilian, barbarian female civilian, Roman hornblower/ flag carrier, Roman Peltast, Carthaginian marine, Eastern merchant, female barbarian warrior, Gladiator, Snake charmer, Gothic swordsman, German hunter, African spearman, Persian archer, Sailor, Persian lady with urn.