Very true points Fahrenheit. I'll try to avoid those for future things!
Just some general critique for all of your artwork as a whole. You seem to have a really good sense for rendering details, clusters, and color choices. The only real crits I can see for your artwork is that they seem to lack some more construction based skills, the perspective's off, the shading is wonky, the pose is awkward, etc. None of those are specific to you necassarily, but those are some things I would try to watch out for in your coming drawings.
Keep doing great work man!
You're really good at making rocks look like rock. Awesome job with this!
Looks good! I like the skyscrapers in the background, coupled with the title gives a nice idea to the viewer. Never know what lies just beyond!
in the weekly showcase and it requires revision :D