Really nice work, love the design of the city, if was gonna suggest anything it would be that the city might be a bit too saturated for the distance it's meant to be, maybe add a bit more atmospheric perspective and then pick out the highlights with that nice gold colour, at that distance and in those conditions (dust and sand in a strong wind) you wouldn't be able to pick out all that detail (not what you want to hear i know!) To avoid losing it against the background you could brighten up the sky to add contrast and really define the silhouette (There's almost a bit too much going on there). I think if you simplified the foreground rock formation and removed some of the bounce light it would nicely frame the city, it's a little muddy where the city meets that rock arch. From the direction of light you could give the rock a nice sharp rim light to really separate the forms. Also the transition on the ground terrain beneath the riders is a bit sharp, you've gone very quickly from very soft to very sharp directional lines, could do with a bit of blending of the two terrain types as the eye kind of stops at the transition and gets stuck. Hope that comes across as constructive, it's a really great image and a brilliant concept! Great work and good luck with the compo!