Know how much space you have. If you have a large kitchen island, then you can use full size chairs. For home owners who only have a smaller one, they may only use two seats. You should also decide the space that your guests can have. Sometimes, kitchen islands are merely used for decorative purposes rather than practical seating. So if you want to add seats, you should make sure that you have enough space in your kitchen for them.
Regarding colors and designs, kitchen islands can be made from a number of different materials. The framework is usually wood, but the main visible surfaces could be metal or even stone - granite is a popular substance used for counter tops. Stainless steel is also good, but try to avoid aluminum if possible, because that is very soft and easily cut and scratched, and the metal oxidizes to a dull finish.
Budget : Setting a budget out front can be beneficial if you have budget constraints. Having a budget to work on, you can easily adjust the types of material to be used or length of wooden planks to be purchased accordingly before ordering the materials.
For those remodeling and looking for an "open" feel where perhaps the wall or half wall separating the kitchen and the dining room is taken down, a strategically placed island acts as a subtle room divider mentally separating the kitchen from the dining room but with a much more open feel.