Couple of suggestions
you can check whether it has itp_wooden_parry to play the wood instead of metal sound, or even play the gong sound when you hit a hero.
Aim at random, different bones to achieve different effects, for example disarming if it hits arm bones & lowering movement/dehorsing if it hits leg bones.
You can also store the item's other parameters to tweak how well it performs, such as
- Use weight to determine cooldown period between uses similar to shield bash, perhaps checking player agility
- Calculate the ratio of height/width of the shield & speed rating to determine how aerodynamic it is (as a modifier alongside ST_Time_Factor)
- Take shield resistance as the min damage, modify max with power throw so it requires investment into multiple skills?
- Add in the unfun chance to break base on shield hp + imod, or even not returning so you have to do a walk of shame to pick it back up