I definately think that a lego mythical range from the legends of classical Greece would be fantastic. Here are some ideas.
Small - range sets:-
Hercules against one of his 12 labours, fighting say a harpy mini fig.
Atalanta (a female mythical)against the giant boar, with a tree set (similar to the forbidden forest in the current Harry Potter)
Mid- range sets:-
Perseus Mini Fig up against a Medusa minifig ( take the snake tail base from the latest ninjago lines as her minifig base. A third minifig could be another warrior alread turned to stone and a small temple backdrop.
Theseus Mini Fig in the Labyrinth with a minotaur Minifig in a labyrinth passageway, pehaps with a hidden panel.
Jason and the Argonauts, with a Greek Galley ship, Jason, Medea, Hercules, Orpheus and two argonaut Mini Figs. It could also have a small Tree set with the Golden Fleece and a lego Hydra monster guarding it.
Trojan War- This Set would have a trojan Horse, a walls of Troy set and mini figs of Paris, Achilies, Helen of Troy, Agamennon, Two Trojans soldiers and four Greek soldiers