Here is a work-in-progress enemy to show you how these guys work. This one's tentatively named "Guilty Christian" and he's based on 16th-century depictions of demons-- little apelike guys made of mismatched animal parts. If you've played the demo you may have an idea of how they fit into the concept / story. They'll be an intermediate enemy between the easy White Ogres and the tougher "human" ghosts-- using humanlike weapons and tactics, but not shields or armor.
For most enemies, the arm holding their weapon is a separate sprite that gets overlaid on the basic sprite, so they can attack in any direction and hold different weapons/items. For a few of them, like the witches or the witchfinder, their attacks don't involve a weapon or emanate from a fixed spot relative to the sprite, so their whole body is drawn directly on the base sprite.
Here's the spritesheet with the basic idle sprites, 4-directional walk, and flickering frames used when taking damage. Generally, if enemies have a 4-directional walk sprite, they get 4 frames per direction, which looks pretty good but is slightly lower quality than the player character (6 frames per direction).
The white ogre, for contrast, has a 1-directional walk sprite that's flipped when his velocity is negative on the x-axis. This is because it takes more frames to emphasize the weird unique way he moves, but also because he's a more cartoony character with a vaguely-defined torso, so the "shoulder" of his weapon arm can always be directly above the xy coordinates of his sprite.
The demon needs a 4-directional walk because his shoulder is in a noticeably different place depending on the direction he's facing. His weapon arm needs to attach in the same place regardless of whether he's moving or standing still, so it doesn't suddenly change positions in the middle of an attack when he stops or starts moving.