id say before you go any further with detail pixel work, i think you should consider throwing a lot more color theory at it and see what sticks.
so youve got this tunnel of light/fire which breathes warmth out onto the otherwise grim, ghastly dungeon-like cobblestone environment. yet the only evidence of the warmth that i see is some minor ambient light blobs being cast on the upper edges of the cobblestone. Take a look at the cooler tones used down the length of the corridor... they share the same purple hue that you are using for the foreground open room area. if you want to give that room back there some real fire, try keeping the shadow tones in the orangish/reddish area (if youre an advanced color user, using a lot of desaturated greens or magentas might lend well here just the same, so long as theyre more grey than saturated). Right now the purple creeps up too closely to the intensely heated room behind the distant door.
Another thing which will punch some life into this to really make the eye catch the heat in the distance is to really darken that tunnel to a near black , particularly in the middle of the corridor where the light from either room isnt able to quite reach very well. its this play of light to very dark to back to light (very quickly) which is going to establish that strong contrast youre going to need to really make this reddish fire look like its searing, piping hot.
In general, subduing the saturation of the purple, more particularly in the mid and shadow tones, would do this piece well, and would help give it more of a natural feel in its lighting.
when i get home ill mock up some examples.