Engine fan blade 'clanking' is indeed normal and when not present 'worrying'. Each compressor (fan) blade is attached by means of a pin or in a dovetail sort of joint called a fir tree root. As the engine spins centrifugal force acts on the blade forcing it outwards. Being able to move allows the blade to find its own happy medium thus preventing vibration. Blades that do not fall under their own weight whilst windmilling ie 'not clanking' usually indicate corrosion and on some very old engines such as the Conway are a reason to reject the engine.
Rippling of skin is known in the trade as 'panting' and is normal - find any photos of B52's to see why, the exhibit at Duxford is a fine example. On the ground the stresses on aircraft are completely different to the forces of flight - lift/weight etc - Skins are normally replaced when the aircraft is stress jacked ie jacked to replecate flight forces, so on the ground the skin may appear to pant.
Hope this answers your question!