This definitely qualifies as a "so obvious, we forget to use it" piece of film making advice.. Loneliness and isolation, are powerful emotions that are often an important part of a hero's journey (Above from "Avatar"). I've found that the most effective way to express this is NOT with direct dialogue, or even an accurate drawing of the characters expressive face, but rather to place the character small in the frame and/or surround that characters by empty space. Above, a story sketch from my new film "Masks", where I used this approach in a very basic way to show one of the characters traversing the exploited badlands of his once lush home.
(Above a classic story sketch from "The Rescuers") It's effective for expressing character's emotions and it's a poignant statement, despite the fact that you're not even looking at a detailed image of the character, just their gesture and their placement within the background. It also acts as an effective establishing shot for the rest of the sequence, putting the sequence into context right out of the gate!
In addition to giving a lonely feel, Andrew Wyeth placed the female character low in the frame, creating an even more powerless position in relationship to the overpowering desolate farmland.
This painting by Kendrick Mar, expresses the same thing in a more iconic context, but the basic idea is there.. small figure, open space.