Sometimes simply finding something you are sufficiently interested in to carry to completion is the actual artistic challenge.
While many scenes might catch your interest, is there enough there for carry though? What might keep your interest for a quick sketch, a 20 minute drawing or afternoon painting will not hold enough interest for what can be days or even weeks in colored pencil.
Like a fine oil painting, working in colored pencil can take time. For a large piece this can be a major investment in time and effort.
Creating a work of art is more than simply copying a photograph. While a good photograph can be a good beginning, each artist adds/subtract, enhances, edits and refines whatever reference material she/he has.
Any work of art starts with an idea.