In the Lego online community, greeblies are the intricate details on the sides of spaceships and sci-fi MOCs that define the mechanics and workings of what the MOC is meant to be. They were famously used in the giant Star Destroyer Lego set a few years ago, and also in the more recent Death Star II set. Plates with rails are often used for greeblies because they have a protrusion that only sticks out half a stud without needing a jumper plate. (source: Brickspace.org)
Bley is a colour of grey used in newer Lego sets. Before bley, the standard light and dark gray colours were used. When AFOLS complained that the standard grays were too orange in colour, Lego started producing bricks in the Bley colour
That MOC had a strange mixture of bley and gray pieces.
In the Lego online community, a MOCer is a term used instead of 'creator' for someone whose hobby is building with Lego. MOCer comes from the term MOC, meaning 'My Own Creation', which has its origins in MOCpages.com
Hey, have you heard of Nannan Zhang? He's a great MOCer.