This is the Reaper, it's something I was asked to design when I was part of the development team for Sodium One (a shoot em up game released on Sony Home for the PS3). The brief called for a great big spider like robot thing make of junk to act as a main boss. Due to the limitations of the HDK engine we were not able to make a walking machine so we had to make do with a hovering one. I put the development tem in the picture too.
Practice practice practice, there is no real secret to it just carry on doing the art, you get better as you go, what kind of film do you want to make?
sci fi look at my stuff its based around genetically engineered people who want to bring peace to the galaxy but things obviously want to stop them i will try to post some background on the thing soon. im currently writing the second book on it