It doesn't matter where you are in your painting journey, creating a series of work is always an important skill to have and if you plan on becoming a professional artist then it is an essential skill. 

You can use the following reference image to create you own series or I hope this will encourage you to find an image that inspires you to create your own series of artworks that work together in a collection.

Working in a series is a great way to quickly gain skills in a certain style or medium, because as you become more familiar with your subject matter you should feel comfortable enough to explore and loosen up your work.