Well now, that's a big question! There are around 20000 herbs on the planet and probably about as many vegetables, so it's not so easy to generalise!
Off the top of my head, I can't think of any herb or vegetable that can't be frozen. But whether a frozen product can be thawed and come out just like fresh is another matter. For instance, parsley and chervil are just two herbs which freeze well, but they are no good for garnishing when thawed because they wilt. As for veges, you'll find that some need blanching before freezing, and some don't.
Peppercorns don't need to be frozen. They should keep for several years just as they come to you.