I live very close to Baton Rouge. I am not sure, though, about the thin piecesof slate. Perhaps if you can find a picture online of what you are referring too we may be able to help. From my guessing what you may be referring too, it sounds like something you could find at places like Lowes and Home Depot. Perhaps you'd even get lucky and find a place that has broken, slightly damanged, or left over slate tile that you could use.
As far as southern Louisiana style (for a bedroom), I would go with wrought iron. This is very "southern looking", easy to find and easy to incorporate with whatever colors you like and/or already have. It's always been my dream to have one of those big iron beds (maybe one day... LOL). I think they look very romantic, old-fashioned but modern at the same time. I have several iron decorations in my house from various places. Just a couple of weekends ago I purchased a nice, sturdy iron basket with flour de lis (sp?) on them from Hobby Lobby (on sale 50% off.. whooohooo!). They have tons of iron items there (crosses, wall decor, baskets, candle holders, etc.), at least in our area. You may want to try there because you can usually catch good sales and their website always has a weekly coupon (sometimes as good as 40% off or better).
I personally like the look of neutral colors (white, toupe, off-white, etc.) with the iron. For some reason, it looks more southern to me and makes the iron more noticable.
God bless and have fun decorating!
Julie