You can tell where his eye should be based off face symmetry, the fact that he has the massive scar is just further proof IMO.
I guess he could be winking at us, but then so could the dragon in the OP. The one which doesn't match any description of Nidhogg, has no visible battle scars indicating any involvement in a 1,000 year war (outside the possible missing eye), and certainly doesn't seem like the inspiration for the Drachen Armor.
If the white dragon is Nidhogg, I am extremely confused. Nidhogg is said to be seething with rage, yet that art work is clearly a meeting of sorts, while the Benchmark Dragon is clearly just an out right battle with a fairly unfriendly seeming Dragon, who is missing an eye, seems much closer in comparison to Drachen Armor, has numerous scars from various battles with (presumably) Ishgard and various Azure Dragoons. If that ain't Nidhogg, I don't know what is.
You can also see the scars very clearly in this artwork, though not the missing eye;
But yeah, of the two which one seems to be seething with rage? This one, by far. The whole seething thing is information we've basically gotten directly, too, since it comes from Nidhoggs Eye (unless our friendly neighborhood Azure Dragoon is lying).