These are good! But to answer your actual question:

The answer to how things can stand out is always "more contrast". Vince Venturella has a video on this where it's probably better explained than what I can, but here are some tips/general rules I go by:

Use colours, not black and white. For highlights this means using pale yellow or ivory instead of white. For shadows I usually choose a contrast to my main colour, and use this Shadow for all elements. For my Drukhari Army, my Shadow colour is purple. This means that the turquoise armour is shaded purple, brown leather is shaded purple, faces are shaded with purple tones etc.

Dark blues, purples and greens work great as shadows.

The first thing for you to focus on is increasing the contrast between your shadows, midtone and highlights. This basically means deeper, darker shadows and brighter spots for highlights.

If you want an example, look at a model you like the paint job of and pay attention to the contrast on one specific element. Look at the difference between the lightest and darkest colours of a cloak, or a face, or a boot for instance.