Pick a countertop for your island that matches your other counters or make it stand out by using a contrasting material. Also, your choice of cabinetry and decorative elements can make your island into a real quality item, similar to a fine furniture piece.
Islands can "float" as well. Smaller islands used primarily as an aid in cooking or baking can be fitted with wheels and moved around the kitchen as needed to aid in cooking. Whether you consider a floating island will probably depend on what you have installed on the floor now, or plan to install (a soft wood will be nicked and scratched).
We are often asked if the countertop of the island needs to match the existing kitchen countertop in style, or what will be installed as the main kitchen countertop. In most homes I would say it does match, but it really does not have to at all, nor does the material need to be the same. In fact, if you are not going to match them up exactly it's better if it looks like you are not even trying to match them, so using a completely different color and surface is perfectly acceptable.
Your first consideration when deciding on a which type of kitchen island you'd like should probably be how you plan to use it and their functions are as varied as the wide range of design options. They can be a utilized as a food preparation area, a baking center, a serving spot for an informal meal or buffet and the perfect setting to sit and nibble a snack or sandwich. An island even can provide a quiet spot for children to do their homework, close to mom while she gets after school snacks or dinner together.