Feature walls aren't just for living rooms and dining rooms, you can create vignettes of interest all over the house and especially in the master bedroom.
Your headboard provides the ideal opportunity to really make an impact in this space; consider oversized designs with deep cushioning, or an overhead canopy in draping fabric for a classically lavish or romantic look.
Above 2 via Coolayan
Mirrors hung in multiples also make great wall features, arrange them over a dressing area for extra oomph!
If modern is more your style, try adding interest to your headboard wall by hanging a contemporary painting above your bed, apply an abstract graphic design, or use a vinyl wall sticker for a quick but effective solution.