Wow, an airship flying through a volcanic wasteland with constant lightning flashes from the ash clouds.
yeah work on the landscape a bit. put bowser's castle in the landscape, and volcanoes erupting the lightning-generating ash clouds and lava channel, make the channel more curvy too. Also, make the airship look broke up like they are in the game.
Amazing work on Mario, especially the hair! Hard to understand then, why you have problems with the background. The ship's front looks somewhat odd and the lava channel needs some more work, I think its just too straight The skeleton koopa is a nice add-on, though.