Good topic. I have been wondering about this as well.
I just completed a project using antiqued brass tacks from Crazy Crow. They were pretty antique looking before I started, but after I annealed the shafts on them, they were VERY antiqued. I would imagine if you started with shiny brass tacks it would have an interesting effect to anneal them as well.
I got that idea from Chuck Burrows at Wild Rose, and he also mentions using hot blue to antique his tacks, so you might want to check his web page and see what his stuff looks like. wrtcleather.com