Traditionally, the painting is a view of the northern night sky from his sanatorium window. Raven was kind enough to point out a quite different interpretation, based on a curious feature on the right edge of the painting.
Enlarged and with a tweak to the contrast.
What is it? As Raven offers...
Great Cthulhu looms darkly as he rises from the sea, causing a tsunami
to rush upon a sleeping town. Detail of Van Gogh's painting "The Stars
Visible and unmistakably recognizable are Cthulhu's tentacled head
with gleaming black eyes; his right arm (from shoulder to elbow)
pushing him up; and the corner and tip of his right bat-wing behind
The thought that one of the world's most well known paintings has a definite R'lyeh-ish aspect may be a bit outré. In that case, this serves as a good example of how a little creativity and a willingness to exploit pareidolia can inject the Mythos into almost anything.