Painted harlequin diamonds are a wonderful design for an accent wall as you see in the picture below. You can get creative with the 2 colors that you decide to use. You can also use a muted glaze or even metallic paint with glaze to give a more modern feel.
Though this next room is not necessarily a nursery, I think it is so cute. I love the white furniture against the pink diamond designs. They used buttons on the edges of each diamond. you can get creative with you want to use. Some use gems, ribbons, gold buttons, or anything else that you think would tie it all together.
If you are a DIYer, then her is a great video that will walk you through how to achieve a painted harlequin diamond wall finish:
How to Paint Diamonds on Walls
In this picture, you will see that metallics were used. I just love how creative it is. Check out that funky lamp!