You could try to re-use the dragon's pallete for the hearts and platforms (for a lava effect, which would cut the shades of grey down a bit). It kinda would give that "burning justice" feel that japan loves oh-so-much. Also, the captive's face looks rather odd as her face looks kinda uneven and displaced with the rest of her body (and the body itself kinda looks twisted from what the shadows of the gown shows), but sometimes re-using palletes can be a good thing, especially for a situation like this where tiles would be jam-packed into that dragon.
You also might wanna give the knight some added damage, so that way it would make it look more believable as it shows the player struggling against a tough opponent, which occured frequently in the days of yore.
You also might wanna give the knight some added damage, so that way it would make it look more believable as it shows the player struggling against a tough opponent, which occured frequently in the days of yore.