Consider function first-
The function of the nursery is the primary consideration for the design. Since baby spends the majority of his or her time sleeping this room, it needs to promote a relaxed and restful state for baby. Choose soft calming colors. This may seem old school but, old school is born out of common sense.
Noone can get a good night's rest in a room that has too much visual stimulation. Baby recieves a great deal of stimuli from interacting with the family, and when awake is often times in the living quarters of the home. It is not necessary to make the nursery stimulating, or highly contrasting in patterns etc.
Simple removable decor-
When decorating, try to have decor that can easily be changed out. As baby grows, the room needs to be able to transition between being the place the baby sleeps, to also being the place the toddler plays. Keep decor simple and forgiving. Avoid hanging pictures on the wall of a toddlers room, if a picture falls it could injure your toddler. Soft decor like posters, quilts, and even the child's own toys can be a part of the wall decor. Just make sure everything that needs to be in reach is in reach and things baby/toddler don't need to play with can not be accessible. Don't under estimate a toddler, by the way. They can be very determined.
Use scrubbable paint only. You'll thank me later. Chose colors that can blend with any decor and always consider that your child grows quickly and will soon not want a "baby" room, but a big boy or big girl room. By keeping the colors fairly neutral, you will have an easier time updating to new decor later. There are many low and no voc paints, (see ToolBase.Org) available that can be used through out the home, don't skimp on this in the nursery. Environmentally friendly, and baby friendly too. For the best paint to use in your nursery see this link: Organic Baby Resource