A triadic colour scheme is used in this illustration, the colours blue, purple and orange that are evenly spaced around the colour wheel. Triadic colour harmonies tend to be quite vibrant, even if you use pale or unsaturated versions of your hues.
Anatomy basic shapes - most people know of these simple drawing rules. But when you are having fun drawing you somehow ignore them, or maybe thats just me? Anyways, i beleive using them more consistently would improve my drawings a lot!