In Cataclysm, Shadowmourne had its appearance changed for the worse. The smokey/misty aura effect on the blade was changed to be a solid jello-like blob of particles, and the weapon no longer shows enchant effects, including runeforges, which is a pretty odd decision for a weapon designed with Frostmourne and Death Knights in mind. Every person I have talked to about this has hated the new look, myself included, so please consider reverting the change. At this point, I would be transmogging the weapon to something else if it allowed me, which is a real shame, seeing how the original was easily my favorite two-handed model in the game.
Curious to hear your opinions on this.
Before and after comparison for reference (bear in mind the Wotlk model showed enchants and runeforges):
https://i.imgur.com/D54ts9T.png