It's less formal than raised panels, but is right at home in a country or rustic environment. Beadboard is versatile enough that it looks good in just about any room in the house.
You can find it in 4 ft. by 8 ft. panels in the big home centers like Home Depot. Usually, the panels run about $20 each, are 3/8" thick, and are made of pine. This is a soft wood which will expand and contract with changing seasons, so paint the panels before you add the bottom and top rails.
The beads on these panels are about 1 1/2" wide. If you want more width, you'll have to by tongue and groove boards and assemble them individually. If you go this route, the cost will be greater, and the installation time will be more, but you have much more choice as to the look of the paneling once it's finished.
I have visited several historic buildings over the years, and the Early American carpenters were pretty imaginative about how they assembled beaded wall panels. I've seen three or four widths combine in a repetitive design; alternating 2 widths; and I saw a room where 8" wide planking was used on one wall and 2 1/2" wide beadboard was on another wall.
Having imagination about these things is all well and good, but the steady, constant repetition brings a sense of uniformity that I believe is what most people look for. Height is another aspect where you will have a lot of flexibility.
The minimum height should be "chair rail height" or 34" above the floor. However, your decorative scheme might be better served if your panels were 40" high, or 48", or 60", or anything in between.
The best thing to do is to make templates or sample pieces out of cardboard or some other inexpensive material. Tape them to the wall and leave them there for a couple of days. Then try it again, using a different height. Decide which you like best, and go with it.
Your top and bottom rails should be notched out in the back so that the panels fit inside the rails and the rails touch the walls. This will eliminate gaps between the rails and the walls.
Some of the most popular ways people use beadboard are:
To cover entire interior walls.
As wainscoting on either interior or exterior walls.
To cover ceilings - inside coffers, over a small portion of a room to separate it from the rest of the room, or as porch ceilings.
As backsplashes in kitchens.
Instead of ceramic tileon bathroom walls.
As recessed panels in cabinet doors.
In conclusion, beaded wall paneling has stood the test of time. It has been around for hundreds of years and is versatile enough to have many applications. Beadboard has good looks and charm, and is priced for anybody's pocketbook.