If any of your children share a bedroom you absolutely should consider purchasing them a bunk bed. It is a rare part of the house that both kids and parents can get equal pleasure from. If you shared a bunk with one of your siblings when you were younger you know that there is something quite special about them that just can't be put into words.
The most obvious benefit is the extra space that can be obtained by installing bunk beds. Some children are initially opposed to sharing a bedroom because it leaves the room too cramped to be comfortable. Simply by stacking the two beds on top of each other you can free up nearly 50% of the entire room. Many units also include some sort of storage space, which you can never get enough of when you have multiple children. Kids need a large area to play and let their imaginations grow. Making this change will allow you to keep the toys in their room instead of scattered over the entire house.
Sure, the extra space is nice but there is so much more to the benefits then just that. Even if you have plenty of rooms in your home many experts would still recommend having children of similar ages share a room. There can be no understating how big of an effect this can have on their long-term relationship. There is a certain amount of bonding that occurs when you share room as someone that cannot be obtained any other way.
While you might be thinking about all the practical ways a bunk bed can improve your children's room, they are just thinking about how awesome it is. Children view their bunk beds as more of a fort/tree house combination than as a place to actually go to bed. Kids will be excited to get into a bed where they get to climb up the ladder to get there. As anyone with kids knows putting them to bed is a exhausting task, so anything that makes that easier is a blessing.
There are thousands of different designs you can choose from. You should be able to find one that matches any room, and there are plenty available specifically designed with child safety in mind. It could even be fun to have your kids come with you and pick out the one they like best.