If you make a quick search for "Witcher 3 Medallion" you'll find some awesome arts with medallions that have Red glowing eyes.
That's not really what we get ingame...

Also the original textures are as low as 128 x 128 so I saw the necessity to change that!

What I did:
Changed the material used in the medallion.
Scaled up the textures.
Made it darker and less shiny.
Added stains and scratches.
Made Red Eyes that glows in the dark.

Clarification about the glow:
The glow intensity changes with the environment.

The glow is more noticiable under Rain weather, Interiors and Caves
In caves the effect is absurdly strong.

Under the sun, receiving light from fire, lightsources in general the glow "effect" will not be very visible.(makes sense)

Install:
Choose just one of the versions:
- Thin Streak
- Rounded
- Dash
- No Eyes

Just extract to the mod folder to "The Witcher 3\mods"

Credits:
GeorgeTziotis for the help with the eyes ;)
scoutbr0 for finding the emissive material
erx for triggering the idea in my head