I suck with pen/pencil, but computer tools make it possible for me to generate marketable work.
For making logos and line-art, I suggest using Inkscape. It is a free vector-art application like Illustrator, but cross platform and FREE, with lots of community support and development. Vector art has clean lines, regardless of how large/small it is scaled.
For grins & inspiration, google image search "inkscape vw" (remove quotes in search).