I had an idea the other day on how to easily create new and interesting lunar monsters for use in the dragonmech setting.
The Pseudonatural template.
I cant remember which monster book its from but the pseudonatural template turns a creature into something from the Far Realm. Based on current monster descriptions of lunar critters, changing some regular creature into a freakish, tentacled horror would allow it to easily fit in with the other lunar creatures. Some of this was also inspired by my viewing of "The Mist", which i highly reccomend as a film, btw.
Some suggestionson altering existing monsters to make them "lunar" by adding the pseudonatural template:
Trolls - Lunar trolls are pale white, thin-limbed creatures more suited for movement on all fours. Similar to other lunar creatures, black veins run in tangles just beneath their skin. A lack of eyes makes them appear blind but they sense their surroundings as well as any other creature. Their faces are round, with an obscenely wide hinged mouth filled with multiple rows of razor sharp fangs, givent their heads and almost 'flip-top' appearance. Spikey, thorn-like hair sweeps back from their foreheads and ends halfway down their back. When hunting or feeding, spiked tendrils snake forth from their mouths, helping to pull and tear at their meaty prey.
Dire Bats - Lunar bats lack the dense fur of their terrestrial counterparts, instead sporting a tough, pale leathery hide. They posess four wings rather than two, making their in-flight movements appear haphazard, though they have no difficulty homing in on medium-sized or smaller prey. Lunar bat's faces are longer, more muzzled than other bats, and they lack feet at all, instead posessing a small tangle of tentacles at the end of their bodies which they use to clasp onto their perches and hang while resting. Like terrestrial bats they live in colonies, but on our planet are more likeyly to be active during the day, when the winds and dust of the lunar rain are less of an imediment to flight.
Just a couple of suggestions...