Some of the skills I've really been focusing on are depth and perspective. Depth is tricky, through value and detail I can push an object closer and farther in the space. The detail level is by far my favorite as I love the way it feels to have a detailed focal point. Perspective has been interesting, for the lava picture I laid out the perspective myself because the shapes were simple enough and I didn't put as much emphasis on design as I probably should have. For the mech image I had Google SketchUp take care or the perspective work for me. Working in 3D really lets me focus on the design. So from here on out I will typically use SketchUp as a base for design and a solid perspective foundation.