I like @kelly's idea of picking a lovely fresh color of paint for the door. You can then bring it down onto the stair risers. Either a solid color to match the front door, or go wild and add some decorative elements to the risers with stencils. Or think of staining the door a great color and coordinate the stair railings and risers. I have an idea book put together for just such project that might spark some ideas for you. http://www.houzz.com/ideabooks/16700983/thumbs/Kathryn-Delany-s-Decorative-Stair-Risers

I just found out that blue green colors really bring out the beauty of wood. I know its not the same but I have honey oak cabinets and just repainted my kitchen a blue green and it really made the cabinets look stunning. Maybe you could try something in that color family to enhance the wood. Just a thought.

Teal sounds beautiful for your splashback, I love vibrant and bright colours in the kitchen - you never see them enough! I think your worries are right as well, dark carpet and a dark bench would be too much darkness - a lighter benchtop would work well with the other colours! Marble is a classic for benchtops, but depending on how you did the wood, it wouldn't look fake at all! What did you decide on doing?

A very simple layout keeping the floor space within the kitchen, the WIP takes up a lot of space with not much gain, The broom cupboard could be moved to the Laundry/entrance, narrow. If the wall has been bumped out to the eaves on the deck side giving an extra 300 depth to the kitchen you could make the island 2700 x 1200 and all drawers. The wall of narrow pantry will hold all pantry needs and more, no deep cupboards to dig into. cheers