Before you start decorating, decide how you want to use this shared space. Most commonly, a space such as this is used as a dining room. But you may want to use it as an office or even a play area.
Your use of the space will determine furniture and its placement in the shared space. If you're using it as a dining area, put a dining set in the middle of it and and anchor it with an area rug. Keep the furniture simple and as casual as possible. Modern or contemporary furniture works well with open-concept designs. If you plan to use the space as an office, add a desk that complements the rest of your decor.
Let the size of the area guide you in your selection and placement of furniture in the living room. Many of these living rooms are compact, so you may want to limit yourself to a sofa along one wall and the flat-screen television opposite it. Keep the lines clean, and do without a coffee table to keep the feel of the area as spacious as possible. If you have a bigger living room, you can consider sectioning off the separate space. Arrange one sofa along a wall, and another sofa perpendicular to it. Or use a low bookcase or buffet to separate the space. Keep these pieces of furniture low so that you can still see into the living room from the kitchen.
You can use one color for the kitchen and another color for the living room and shared space. Or consider using monotones such as white, black and gray. This is especially effective if the space is small, and your tastes are modern or contemporary. A complementary color scheme also works. For example, use terra cotta in the living room and green in the kitchen. Or use yellow with white trim in the living room and blue with white cabinets and trim in the kitchen. Pull all the colors into the shared space. Choose a patterned carpet, as well as accessories that have the complementary colors. This will enhance the separate identity of the shared space but also make it look like part of the whole.
No one says you have to give that shared space a separate function. If you have room in the kitchen for a table and chairs or an extra bedroom that you can use as an office, consider using the living room and the shared space as one large area. This will allow you to bring in larger and more furniture, such as a sectional sofa and tall bookcases for your photos and artwork. The space is yours to use as you please.