I've been told you want to have a lot of concepts/designs to show, so the second picture is a better example. It's good to show something refined like the first picture along with a page of sketches/design variations/props for it. https://www.artstation.com/artwork/DQD69 I think this is a good example from an artist who works at riot. Also, you can look at the art on the wall inside of brainstorm, the examples are past the vending machine and those pages have great layouts for a portfolio. I hope that helps!