Have you considered using stencils on your walls? This cute sunshine stencil can make a cute pattern on a nursery wall. Much more affordable than wallpaper! Use one or more colors for an interesting wall effect.
**this stencil includes a set of 3 graphics spaced evenly apart. (approx 12" - 24" apart depending on which size you order. ) Paint in the graphics and then move the stencil over; overlapping one of the shapes to help keep the same spacing