When selecting artwork, first and foremost consider the style of the room and select pieces that either match or compliment that look. In rooms with modern furniture, for example, pure modern pieces and frames maintain the theme for an extreme modern feel while traditional ornate pieces provide a more eclectic look. Pay careful attention to the frames when going eclectic in a modern home so you can push the overall look of the piece far enough into the “ornate” category for the choice to appear intentional. Traditional homes can also incorporate a wide variety of art styles, but in this case, the framing should be kept within a more traditional theme for consistency within the home. There is nothing I love more than a cubist style painting framed within a huge rococo frame. The choice seems wrong, but it does pack a punch in the room when it is done correctly. In cottage style homes you can enjoy a wide variety of art styles so long as you keep the framing selections somewhat consistent. In my home, for example, while the frames differ in style and size, they are all painted black. This allows for a nice flow throughout the home even when the subject matter and color of the art changes from room to room.
If the artwork you are selecting is to be part of a grouping, you should decide whether the pieces in the group are to be part of a consistent theme and style, or if the collection will include pieces of varying styles and mediums. Artwork groupings of a rigid theme and color palette can be used to enforce the sense of a particular style in the room as shown in the photograph above. Filling an entire wall with all black and white photography can create a sense of unity in the group even if the subject matter differs from piece to piece. Color photography and artwork can also make a nice statement when a specific color is chosen and repeated. When framing an eclectic grouping of pieces, make sure to keep the framing consistent so the wall does not end up looking cluttered.
The color of the artwork can (and should) be chosen to compliment the room. I like to choose pieces that fall into the range of my main accent color to give the room more definition and allow for the eye to more easily move about the room. If you have more than one accent color, both of those colors can be incorporated into the artwork if you choose.