I found this watercolor illustration and thought it did a great job of showing perspective in art. This isn’t a vector, but I think the same principles apply. If this was done poorly it would feel awkward and it would be hard to tell what things are behind each other and which ones are right next to each other. Here are some things that help make this work:
The first thing that helps this painting is the coloring of things. You can see variation in the coloring that helps in seeing perspective in several parts, but I chose to show the gray wall on the right-hand side. At the bottom, you can see the wall is a very very dark gray which gives the illusion that it is behind things. Some of the other grays are similar in color but because there is a stroke, you can tell where one ends and another begins. When the walls are behind or in front of each other, they are not the same shade of gray. This helps give depth.
In the diagram above, I have copied the same exact blue line on all three pillars. You can see how each pillar behind the tother gets thinner and shorter. This helps show that they are getting further back and creates more depth.
Lastly, the artist used perspective. You can see the vanishing point in this illustration. Everything on the edges is created at an angle. The wall to the left, which could be seen as a rectangle, is really more of a trapezoid to follow the vanishing point and give perspective to this piece.
See the rest of the paintings.