This traditionally styled painting is deliberately sombre, dark throughout the background and only applying light to the subject's facial features. Even his own clothes are hard to pick out. Other portrait paintings by Van Eyck would also show off his skills in depicting clothing and material, but he keeps this work fairly simple.
One can just about make out some elements of fur around the edges of his coat and sleeves, with his hands just encroaching into the foot of the painting. He holds something in his fingers, perhaps a ring or a button from his coat. The quality of the image here is not quite good enough to pick out what it is. Whatever it is, there is most likely a symbolic value to it, perhaps indicating the status of the subject.
Considering the fur within the subject's clothing, perhaps he was a reasonably well established individual who could afford to commission this artist for his own portrait. Alternatively, perhaps Van Eyck simply saw something in this man's features that encouraged him to persuade him to model for a portrait which was purely for the artist's own interest.