Hello,
a couple of years ago I stumbled upon a post by someone who had made a tutorial on how to switch decals using bones that he would rotate. So for example, if the bone is pointing up, a smile decal is shown, and if it's pointed down, a sad mouth decal is shown, and then you could have any number of decals inbetween at different angles of the bone. I think the bone was just placed somewhere random, it wasn't necessarily part of an object. The setup may have also included the use of expression sliders. I remember the guy who did the tutorial had an accent, possibly latin american. I thought it was very clever. I know that the always inventive johnl3d did something like this, but the tutorial I'm thinking of was a little more involved and definitely by someone else. Does this ring a bell for anyone? I thought for sure I bookmarked or downloaded it, but I can't find it anywhere. Would love to see that again, as it might be useful for a project I'm planning.

Thanks.

I'm pretty sure you are thinking of Marcos Rezende's Smartskin-influenced Decals. (He's known as 'Xtas' here in the forum)
The main tutorial is on his website but you'll find interesting information and commentary and such from the usual suspects here:

http://www.hash.com/forums/index.php?showtopic=33460

A direct link to the tutorial:
Using Smartskin to Animate Decals

That was it! Awesome, thank you! I see that I even commented in the thread, yet I couldn't find this post... anyway, thanks again Rodney, and thanks again Xtas -- that tutorial is great.