If you need to keep the space open due to light levels, then shelves with an interesting display would work well, a glass divide/window can look odd on an internal wall, if you are not careful, although, depending on the rest of the house, the crittal window might look interesting too. Stained glass would have to look good on both sides and could be very expensive. I like the look of the climbing rope diy on the stairs, it might be worth trying that idea too. Please don't go with the fish tank, horrible expensive out of place smelly things in a nice clean home, they remind me of pet shops! It really boils down to what you like the look of best, if you really have to keep the space open, just don't forget there is nothing wrong with feeling warm in your home and there is more chance of that if you don't feel a blast of cold air every time the front door is opened, so don't rule out a proper wall if it at all possible.

Thanks @minipie. I am looking for something full length + would like to have some storage (height same as that of kitchen worktop) on the side of the kitchen. On the right side of the kitchen, we have some decent dining space (280cm x 240cm). I would also like to consider building a wall type divider with a small square window , however not sure how this will look. :/

Looks like the panel is glass, though it has some kind of texture to it that will make it less translucent and gives that shimmer where the light catches it. It might be a double glazed unit as well - which would help with noise control if you need that. The thin frame is a kind of metal, perhaps a bronze or bronze effect finish. It can be that thin because it is internal only so it doesn't need to deal with thermal stuff like a sliding door in an external wall would. Hope that helps! Jane, i-architect.co.uk

Our original layout was a through lounge and dining area. I didn’t like it. I preferred to shut the lounge off and then knock doen the existing wall between the kitchen and dining area which is what we did so we have a kitchen diner all across the back of the house. We then put double doors between the dining area of the kitchen diner to make the lounge private. Closing the double doors keeps the lounge warmer in the winter but we tend to leave them open and only close them when we go away so passers by can’t see through from the front of the house to the back.