There are a variety of methods for communicating depth and scale within a representation. The most effective way to do so is to bring in entourage. More specifically, populating a representation with people.
Scaling people as well as changing the opacity of the these people will help show how far back the scene moves and what the atmosphere is like. Play around with this for a while. Try black or white silhouettes. Change their transparency. Try an image that shows their clothing. This can help speak to season or the weather. Look at a variety of other peoples work to see how they communicate and what they are trying to communicate.
CLOG, a on-line/print publication, wrote about how observers of these images often look for/at certain points in an image. Professionals tend to look at the designed pieces while the layman observes the entourage. This being said, know the crowd you are marketing your work to and how to reach them. While the people may not be the highest priority to your design, showing the investor how people interact and function within the design may just land you the job.