Lots of specific threads out there on pieces, exhibitions, or artists, but couldn't find a general one (despite Josh's of the same name). Feel free to add any more subsequently.
Saw these fantastically detailed pieces from Brooklyn's Mu Pan, in which he puts traditional Japanese kaiju in the scenes of famous historical battles. More available on his website
here. Small pics here, but I strongly urge you to check out the embiggened versions, so much extra stuff to see in each of them.
Gamera c. 1943
bad-ass detail
Godzilla vs. Giant Squid c. 1894
ferocious close-up