Previously, his subject matter has been primarily concerned with a navigation of an interior, metaphysical territory. However, Aitken's latest work has begun to look outwards more, encompassing wider issues and world events. Consequently, these images have begun to reflect an increasingly emotive space where tensions and anxieties found in the outside world have begun to be explored.

In these works the natural world and evolutionary theory have been influential, and Aitken has become increasingly interested in representing the physical appearance and structure of the human body. Silhouetted figures have acted as a motif to convey metaphorical topics of both a religious and secular nature, and a series of heads have combined different stylistic approaches to portraiture that reference the precision and realism of Victorian anatomical engravings, with the graphic shorthand of cartoons.