Some quick Mace spec Ideas:

Bonham: You are a master of the drum, you actually hit the super rare fifth strike much more frequently. **WOULD LOVE THIS ONE**

Bitch Slap: You have a chance for your Backhand to catch them twice once on the back swing and then once on return.

Thiesman Special: Your bone shatter has a chance for the broken boke to break the skin causing serious bleeding.

Crunch time: Your denting causes metal armor shape to warp making it harder for the wearer to manuever in it until they have time to remove it and put it back on.

Dents and dings I think this could even be given to dent just as part of the skill to make it worth using more often) By denting your opponents armor their AC for that piece of armor is reduced to 2/3 for a long period of time.

Speed Drummer: A missed drum only costs one round of combat, and a wimpy two hit is only two rounds.

Fat Lip: On a sucessful backhand there is a chance to hit the opponent in the mouth causing it to swell up for an hour or two. Making it hard or impossible to speak.

The names suck, but I think this will help spark up the lack luster mace.

That which does not kill us,
makes us stronger.