When you have a kitchen already in place, it can be hard to think outside the box and decide what else you could do with it. The chances are, you may be able to lay it out in a different configuration that will give you more space for the things that are important to you, like an island, or more worktop space.
The way to rectify this is by obtaining a professional kitchen design. The designer will use the measurements of your actual kitchen to see what will fit in, and where. They will then produce a CAD design for you, so that you can see exactly where everything will go and begin to visualise it in your mind.
You can get a kitchen design from most major kitchen retailers, however remember that they will be using their own products, so you may get a slightly different design if you go somewhere else.