When choosing the theme for a nursery you need to think about the lifespan of the theme that you choose. If for example you have chosen a nursery rhyme theme, consider whether your baby will be happy with the décor when it grows into a three or four year old toddler. Think about whether it will be an issue for you to redo the room decoration every couple of years or so.
If the lifespan of the themes is important for you then select décor that is less babyish. For example you could use an alphabet theme or jungle or farmyard animals to keep it not only gender neutral but a theme that will last a good few years into the toddler stage. If you know the gender then there are certain boy themes that will grow with the baby. For example you may choose classic cartoon characters, superheroes, a jungle or forest. More girly ideas are flowers, gardens, tea parties and fairies.
There are different ways you can introduce a theme to a room. The bedding is one way of introducing a theme. Another cheap way is using borders and transfers. These can be easily removed and updated at a later date. Another idea is to use prints and pictures which again can be updated at a later date.
Let friends and family know about the theme in the room. This may inspire them in their search for baby gifts.