To start the piece is beautiful, with amazing balance. I enjoyed your use of shadow, though I think the highlights could have been a bit more pronounced. The focal points are well defined and the eye can easily move around without feeling stuck. For a dark piece you did a good job of adding warm colors. I especially like the detail in the clothes and armor. What happened to the hilt of the sword? It looks a little rough next to a shoulder pad that is extremely well shaded and highlighted. If I had one complaint it would be in the guys face, or lack there of. It looks undefined and lacks depth. My favorite thing on this piece would be the use of color. The warm tones of the characters against the cold background really make the focal points pop. My least favorite thing is the lack of detail in certain areas. It makes it feel unpolished in places. Never the less - Great job! is very inspiring and beautiful.
You got the girl right, the hardest part. Nice brush work and dramatic lighting. Deceptively simple background too. And the sword chain is convincing. Overall, looking good!
Let's move on to her boyfriend. First, while we're definitely seeing the girl from a low angle, the guy's torso looks either straight on or slightly from above. Changing the angle on those will make them sit right with the sword arm and sword. As another critique pointed out, he needs more definition in the face. I also want more clarity on how his hand is holding the snowboard-sized sword and how it's resting on his back. The negative space between his arm and the sword is murky so defining that could help.
That's it. And don't pay too much attention to the star ratings. dA requires them even though they're not a great way to evaluate work.