Off the top of my head; since Dragons are supposed to have a sort of "Scale" to their skin... you might want to take some leather swatches of various states of soft/hardness and twist them in time with the dragons movements to create a sort of creaking skin/scale sound.
A piece of leather that's wet and left out to dry will have a bit more squeaky resonance than a softer piece of leather. You can usually buy a whole side of leather from a local shop and then treat it to different forms of soaking, different soaking materials (Oil vs Water or Oil and Water ratios vs various drying times or drying conditions).
Record those sounds at 192/24 and that way you can pitch them down and get some depth to it, especially when layering.
You might also want to record some "sliding" sounds across different types of surfaces to layer on the "creaks". ie: slide a book across a table and maybe apply a filter/EQ sweep to it to give it some motion, then when it's in your mix, pan appropriately.
Ok, good luck... let us know what you ended up doing and how you did it!!!