In the section on BSB in the Army book, the page with heroes. In that box it will have a blurb on what the BSB can and cannot take. For example, the dark elf book says a BSB can't take a shield or a 2H weapon, and if he takes a magical banner can have no other magical equipment. VC BSBs have no restriction, except for the magic banner vs equipment one. They aren't special in that regard, high elves can as well. I'd have to check around, but I think all of the 7th Ed. rule books out thus far make no comment about shields and 2H weapons for BSB.
In 6th Ed I used to always joke about how I wanted to downgrade my BSBs to unit standard bearers so they could use shields and 2H weapons. Funny that a hero is so heroic he has less ability then a rank and file.