Designing Titans

I wanted to create a sort of epic scene for a art gallery show a while back the best thing that click for me was the word "epic". With such a word peeking my interest I was thinking of something with scale and what pops into my head... Giant Robots of course.
But in all seriousness the thoughts I consider when designing my piece was:
1) How do I show off the scale I am trying to emulate?
Give off visuals that show the scale like putting in trees what I did, people looking at the piece when get a trigger in their mind to notice the size. Show more and tell less, the more you have to explain your artwork the more you need to improve on (unless you are making a comic).
2) How can I make the robots different but not in style?
I did many sketches before the final I kept in mind basic shapes so each robot all had the same theme but change aspects of each one. They are only robots but they are all characters and should all have their own personality.

The point I bring is you should question your art before and during the process and even after you finish it as well. Breakdown and plan every thing it is tedious at times it can get you away from actually doing your art but it ultimately improves it overall.