Here are a few examples of marker renderings that I have done for various clients, most done under the pressure of a deadline. Often ad comps and storyboards have pretty tough deadlines that must be met, if you don't work well under pressure this is not the occupation for you.
A word you'll become very familiar with if you work in the ad biz.
I did a series of these for a Chicago ad ad agency. This was before I had a computer and I would either FedEx the renderings or take the train in to Chicago to deliver the job.
Often the renderings were loosely done because of the time restrictions. These are all marker renderings done on a high quality layout paper.
I can't remember which ad agencies any of these renderings were done for. These assignments usually had several comps to render.
Some were even fun to do,
I developed a free, fast style so I could belt these out quickly. Often the ad agencies would require me to work in house. I used to get called in to work at McCann Erickson in New York for a week or two to work on premises.
...and sometimes there were changes and corrections, not all clients would pay for these.