I had another go at trying that different idea from the other day and the second attempt was slightly better than the first...
I found it a bit tricky trying to make the owls look not-flat while also trying to keep the dark silhouettes for the "skull" shape and trying to contrive something for the "teeth" was relentlessly awkward.
I still think there's a good picture somewhere inside this idea, maybe with a different composition, but my spacey moonbase seems much closer to being finished so I'll probably be sticking with that after a bit more finger-painting.