I’m far from being a photography expert, but I do have one trick. (This is a music-related post, I promise.)
In general, good photos take advantage of the eye’s full light-to-dark range. In other words, the very darkest part of the photo should be very black, and the very lightest part should be very white.
Here’s a photo that doesn’t meet those criteria—the darkest and lightest parts of the photo are both sort of medium-grayish.
But a quick “auto-level” procedure in photo-editing software (like the free Gimp) corrects this by adjusting each pixel of the photo, basically making the dark ones darker and the light ones lighter:
Even for a photo of a predominantly light- or dark-colored scene, this kind of contrast, applied thoughtfully with a discerning eye, can really make a nice improvement.
Sometimes written music has some of the same problems as a washed-out photo. For example, a composer (or editor) might mark the softest part of a piece at mezzo-piano, and the loudest part at mezzo-forte. The musician must ask him- or herself whether a narrow dynamic range is really the intended effect, or whether the dynamics should be stretched to take fuller advantage of the ear’s soft-to-loud capabilities. (Bear in mind that mezzo-forte and mezzo-piano are not absolute positions on the volume knob—they are relative.) Composer intent should be part of the decisions about how loud or soft each marked dynamic should be, and so should personal taste and interpretative style.
Other musical elements might be stretched to include a fuller spectrum, too. Consider tempi, tone colors, articulations, phrasing, and everything else that brings variety and contrast to music. Spend practice time exploring and expanding the limits of each aspect. Don’t settle for medium-gray!