Well, in reality there is no "practical" size for a kitchen island. This really would depend on what you plan on using it for. In my opinion, the size and layout wouldn't be sufficient to place an island without seriously crowding the kitchen. Can you provide a rough diagram with some basic measurements, maybe we can see what you have to work with.
[B][URL="http://www.corkflooringpros.com"]Cork Flooring[/URL][/B] - [B][URL="http://www.ventless-fireplace.org"]Ventless Fireplace[/URL][/B]