well, the thing he wants isnt nearly as involved as those samples you posted above. it probably wouldn't even take an hour to throw together for someone like you. is there no chance of him commissioning you to make it?
if you are not wanting to sculpt as much, couldn't you use the darkness fig accessories? They are poseable, but the D&D or minature game pieces would work. Or there is also the Medusa fig from McFarlance and work with one of them.
I know it sounds obvious, but sculpting little stuff is just like sculpting big stuff, just on a smaller scale (most of the miniature sculptors I know use "Green Stuff" a two-part epoxy modeling compound similar to Aves.) As far as pure customizing goes, there are any number of potential tiny base figures out there that you could use, either stand-alone figures or accessories for larger figures. If you want to make a small Gargoyle, you could just get yourself a Dungeons & Dragons gargoyle miniature and repaint/tweak that--there are many other D&D monsters you could mix-and-match pieces from to create a gargoyle with as well.