FW could me the next faction I try since I already have x2 common-legendary UD champs, just missing x1 half of the spells, equips, relics which I will never use but I just want to know how many possible themes can be created in FW. So far I tried skeletons but I didn't like it. Skeletons Vampyre/Bleed/LifeSiphon Witches Spirtis Worms Cheap Meat Zombies Liches Soultap Anything else I don't know about?
Check the stickied Themes thread. It covers a lot of stuff, with examples. Two more you should try are Essence Devourer and Chopping Blocks. Those runes are unique, and thus demand careful attention while playing and building. I think Blocks have an iffy position in the current scene, but Devourers can really take over a game, especially if you tech out the BG.