Some Ideas.
For an Italian sausage you would usually use crushed red pepper flakes. 1 Tablespoon for 5 lbs is a good place to start. Most hot recipies call for a couple of Tablespoons of Paprika, to give the sausage a nice red color.
A couple of cloves of fresh garlic, crushed and minced, perks up any kind of sausage.
A cup of wine wouldn't do it any harm either.
For a summer sausage or a smoked "Beef Stick" type sausage , I like to add 3 Tablespoons whole mustard seeds. Edit- This is for a 10 pound batch.