The vision this picture creates as a whole is absolutely hilarious! Hiccup running from Toothless, with only one outcome (Toothless getting the fish). The colors aren't vibrant, but that's okay because that works well with the world you're taking the characters from. It still manages to draw the viewer in and imagine what is going on.
Now the idea of a pet/animal chasing the owner/human isn't a new one. I've seen plenty of pictures detailing it, but this one gets points just for doing it with my favorite dragon! Of course the look on Hiccup's face is priceless, and it's obvious this wasn't intentional (the chase), which adds a bit to the originality.
I can't really say anything in the way of technique other than WOW! You can see each individual blade of grass, the fur on Hiccup's vest, and Toothless' scales. Amazing job on technique. The wings seem slightly more rushed than the rest of him, but that's okay, it still looks great.
Impact, as I've already said this picture really gets the viewer's imagination working. How did this situation start? Is Hiccup going to keep the fish away from Toothless? Will Toothless get the fish in the end? Art that makes you consider what's going on leaves the best impact in my opinion. Great job!!