i’m not an expert, i’m merely a learner
when it comes to big scenes, here’s the tutorial to end all tutorials, it’s well worth the read
same techniques also work in smaller scenes though. style is important. i’ll show an example with a shot that i wanted to be painting- or portrait-like. note that these lighting layers have been edited slightly.
first one is a soft lamp from above. i put it at such a steep angle compared to the camera to illuminate the character while also bringing out its geometry, avoiding a flat look that you’d get if you pointed a strong light at him straight from the camera’s direction. i edited this light layer slightly, overlaying it with black to give it more contrast.
second one is from front and below. i wanted to give the illusion that the ground or what passes for ground, cropped outside the frame boundaries, is covered in blood and gore, so the bright light from above is reflected back up and around the scene in red. this also creates a nice red-white color contrast, which isn’t as cliché as something like blue and orange. the layer was originally uncolored so i tinted it red in post. if we’re talking in three-point lighting terms, in this shot the red plays the role of the “fill” light, ensuring that the areas untouched by the two main lights are not left too much in shadow.
when we combine the first two lights, the result looks like this
it works, but the left side of the shot is left a little too much in shadow against the black background, and it’d be great to be able to tell at a glance where the character ends and where the black void beings. for this i added the third light that gives the character a sharp silhouette against the darkness and balances out the bright light source above the scene
when combined with the third light, the final lighting setup looks like this
what you were doing in the Alien shot looks rather similar, but the contrast of the lights needs to be more tightly controlled. i might’ve lowered the pink light’s intensity just slightly while moving the blue one further behind the creature for a good rimlight effect. it also appears you don’t have a “fill” light in the shot, so the areas between the blue and purple lights are left in darkness, creating a contrast that obscures details and geometry.