This is worthy of a 5 because the banner is well-done, but the model feels unfinished. If your chapter is black and white (Black Templars, perhaps?) it need not be pure black. Boltgun Metal is your friend; take advantage of it! Drybrushing a little BGM on things like the inside of joints and rivets in the armour and whatnot really spruces up a model. Your painting is solid, do more of it!
I'll go with five because I actually like the banner's look and feel, it really does look like its cloth and whether intentional or not, I think its interesting. Some more highlighting on the raised areas and the face would help though, but well done, good effort!