The only changes I see you did is recolor the armor, add green lightning bolts on everything, and a few details her and there, mainly the skull on the chest and shield. The face definitely needs more work, the portrait of a unit is just as important as the unit itself in most circumstances. The model only uses the face down to the nose, but the flat purple color it is right now doesn't say death knight to me, I'd go as far to say its to intensely purple for a night elf.
Change the underlying armor style to your own design, drawing lightning bolts over Blizzard's work doesn't count as much freehand work. Something much more interesting could be done with the sword as well, runes, frosty/unholy/bloody effects, something. The captain's sword with a green center instead of gold is very meh.
Also, the armor patterning seems to end rather soon on the helmet, just because the wing design ends their on the original skin does not mean it will work out ending their with the lightning motif.
But basically this skin is a re-color, if you want to get it approved change the armor you are putting the lightning on top of. Also, for future reference you should save surface details such as the lightning bolts on a separate layer, so that you won't have to completely re-do them every time you need to touch up what lies under them.
Approved
