CASTLE has been going for 3 years now, and most sub-themes hardly ever last longer. i know you need a new line so here are some suggestions
Biggest new set:
Camelot: a $100 castle with 4 guards, 2 knights, 1 king, and a soilder and knight of a new "Black Knight" or "french" faction.
The moster's den: a burp-dark grey-cave with tower on top on a 32x32 area (for about $50-$70.) Perhaps 4 camelot knights/soldiers and a dragon or monster
Farmers cottage-a civilian hut with small field and cart ($50) include farmer, wife, son, maybe animals from Medivial Market village
Merrymen camp-A tree/tower with a tent like in indian jones Jungle Duel. Also include 4 merrymen and 2 camelot knights/soilders ($40)
French Men/Black knight outpost-a castle in likeness to Black Falcons Fortress. Include 4 FM/BK soldiers/knights and 1 camelot knight ($40)
Camelot Cart-a wagon for camelot. Fair sized, 3 camelot soldiers and 1 FM/BK to go with it
The joust-A joust set with queen, king, and knight of camelot and 1 FM/BK knight ($20)
Camelot catapult-a redo of dwarf mine defender without the spikes. 2 camelot soliders and 2 meerry men soldiers($10)
The peasnet cart-($5) a peasnt cart with a peasent and a few accesories
FM/BK and Camelot impulse packs. "the knight" set, but for the two main factions (no more than $3 each)
Merrymen boat a ($5) boat with two merrymen, a tree, and a FM/BK soldier.
Year one: use the Camelot and FM/BK faction in a few sets, but no Merrymen
Year two: Unleash the Merrymen and peasents apon your fans! make up your own sets to sell to finish year two
Year three: using my suggestions, finish off the last year with some thing new: netrual knights with diffrent symbols in smaller sets while keeping the other factions running strong
Camelot-this faction uses red/gold and red/silver color sceme to gain variotions within a faction symobol should be updated crusader shield
French Men/BLack knights-this faction uses blue/gold and blue/black sceme with fleur-dil-lis symbol I do not know what to call them so change the names of any of the recomended factions as you wish
Netural kight symbol ideas-bear, wolf, eagle, snake, dragon, unicorn, bull, etc...
knight means man with euro armor and usually a horse. The merry men do not get these types of men
soldiers means man without euro armor and never a horse.
BURPS-big. ugly. rock. pieces.
Do not overuse the king
include bonus weapons and euro armor often, to convert other minifig torsos into castle-sutable characters
hold the merrymen and peasents till year two as the second blow.
even in the MONSTER'S DEN set, don't over kill with oversize pieces
try to have every netrual knight get a horse.
TO CC READERS
add on and post your own related sets as you wish