Sorry to say but: A year of experience isn't that much. Especially not so with pixel art unless you're extremely talented.
I'd say the average pixelartist is only ready for such sizes after 4 years or so.
Anyway, here's my two cents:
For a dark lord he's hardly conveying any vibe. He doesn't look very dark, or evil. He's just kind of zombie sitting on a throne.
You want something as menacing as a darklord to have alot of pressence and make it all look very dramatic.
One thing that can help achieve this is an interesting perspective.
Your current image is hardly exciting. It's because we're just look straight at him, like he's a normal guy sitting on a normal char.
It's very undynamic, and very uninteresting. Here are 2 suggestions for you. The one a bit more extreme then the other but it illustrates my point.
And for inspiration:
http://www.pcpowerplay.com.au/games/images/news/0809/lichkingdate.jpg