I came across these really cool before and after pictures from Larson Juhl's website. They are great examples of the impact that framed art has on a room.
Framed art makes a dramatic change in each of these spaces shown here. It can be used as a strong focal point or a subtle accessory.
Avoid heavy frames over dainty furniture or petite framing over massive furniture to create balance. In small spaces avoid overly dramatic art that is best viewed from a distance and in a large space choose a piece that can be seen and enjoyed from across the room.
Pairs can be hung side by side or one over the other. Consider the wall space when making your decision. In rooms with long walls and low ceilings, hang them beside each other. In a two story room to fill some of the vertical space, hang one on top of the other. Pairs do not have to be placed immediately adjacent to one another. You can hang one piece on each side of a mirror or tall piece of furniture. Pairs can also be split to become the outermost pieces of a grouping.
Matched sets of framed art are usually framed identically and hung in an organized fashion on the wall. These types of groupings often end up in a grid with perfect spacing. Stairway walls are wonderful for displaying sets. Simply shift your rows so they progress up the wall at the same angle as the stairs. You can also divide sets. For example, hang half on each side of an armoire.