From the Gensou Hyouhon Hakubutsukan (Museum of Fantastic Specimens),  an online collection of creatures by Hajime Emoto.

(Source: pinktentacle.com)

As imagined by Whale, actor Boris Karloff, and a variety of other technicians, Frankenstein’s monster resembles a human battery, with two plugs memorably sticking out of its neck for handy recharge. This design functions as a ghoulish joke as well as a succinct illustration of the egotism of Frankenstein’s determination to render humanity quantifiably mechanical.
Chuck Bowen, the Atlantic - Why Aren’t Movie Monsters Terrifying Anymore?

Artuš Scheiner (Prague, 1920s)

Artuš Scheiner (Prague, 1920s)

Nereid and Triton, from Curious Creatures of Zoology by John Ashton

Lamb-Tree, from Curious Creatures of Zoology by John Ashton

This book looks amazing:

'Sea Monsters on Medieval and Renaissance Maps'
by Chet Van Duzer

Associated images:
http://bibliodyssey.blogspot.fr/2013/08/map-monsters.html

[L]: “A single-horned aquatic bull from the twelfth century painted ceiling in the Church of St Martin in Zillis, Switzerland.”

[R]: “An aquatic elephant, probably intended for a walrus, from the twelfth century painted ceiling in the Church of St Martin in Zillis, Switzerland.”

Lovely crowned creature in tableau at the Museum of Fine Arts in Lyon, France.

Detail with triton at the Museum of Fine Arts in Lyon, France.

Monstrous detail on crossbow at the Museum of Fine Arts in Lyon, France.

Plate at the Museum of Fine Arts in Lyon, France.

Head of a lion, with serpentine tentacles for legs.