From what I understand the L shaped halls are both 18 feet in length. One L has an entrance door across from a window & opening to a balcony balcony and 3 bedroom doors staggered on both sides and the other L is connected to an open kitchen. The window-balcony area sounds beautiful and that is the focal point for that part of the hallway.
These hall floors and walls are going to receive a lot of use and abuse from those going to & from bedrooms and kitchen. The flooring should be of good quality so it will stand up to the heavy traffic. Carpeting, hard wood, slate or tile: it's your choice but again quality is key. Carpeting in the hall helps decrease noise & is soft underfoot and I would choose carpeting. I like a plain color, with a pattern cut pile so it does not show wear and tear. I've had good luck with Stainmaster. I would train myself and family members to remove shoes & wear slippers in the house. This will help keep carpet clean. http://stainmaster.com/page/our-carpets/styles/pattern-cut-pile

The walls will receive hard use, too, so they might be painted in a quality washable paint (eggshell?).

Long halls can look a little tunnel-like: place a wall-art at the end of any long hall. The wall art at the end of the hall will seem to shorten the tunnel-effect and will make the hall more interesting. Choose a rather large piece of art that is bright and cheery. Here is a photo
You could also buy a wall decal for the end of the hall: you place the decal on the wall and it also comes off with no residue. This decal is large bright and fun, but this company (& other decal companies) have many to choose from http://dalidecals.com/Framed-Wild-Flowers-Printed-Wall-Decals-Stickers-Graphics.html

It seems people will be passing the bedrooms on the way to the kitchen quite often. If you're having guests, think of keeping the bedroom doors closed, in case the bedrooms are a mess. ;-)

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Stand in the hall and look into the kitchen. What is the first thing you see? This is probably the focal point of the kitchen-hall entry. Be sure to have this focal point area neat and attractive. Upload a photo or send another description if you want to discuss this kitchen-hall focal point or discuss how the kitchen relates to the hallway and the rest of the house.