Lace is very feminine so it's perfect for girls room decor. It's extremely inexpensive. It used to be popular in a lot of other decorating applications. However, there are a lot of different ways that you can bring this into a girl's room.
Really the type of lace that you choose is going to determine whether your room feels elegant or country. If you want a country kind of look then go with a basic eyelet lace. These curtains and bedskirts are easy to find and quite inexpensive. You can coordinate it with almost anything.
You can find a lot of unconventional ways to use this very traditional material. It is so inexpensive. You can just find a lot of lace window curtains that you can repurpose into other pieces. For instance this could even be a simple solution to closets that do not have doors on them. It can also be a way to make a very romantic looking canopy inexpensively. This is going to be a little bit more intimate and country feeling then the basic white sheer canopies that you see a lot of.
A more sophisticated lace is going to focus more on a netting kind of design style. It may just have very subtle floral accents. You can even find it in a black. You could do this as an overlay on some of your throw pillows. This is a great way to tone down really bright neon colors.
You can also use lace patterns in very unusual ways. In this case try a faux painting treatment where you lay lace against a piece of furniture and then spray paint over it. When you remove the lace the pattern remains. This can be a little bit difficult to achieve but with a little bit of practice you can add a lot of interest to your drawer fronts or a desktop. The one disadvantage to this is that when using spray paint it is very difficult to get an even application. It might be better suited just for use on small areas.