Hi Carolina I have these floor tiles and a similar wall colour, and lots of art. My stair carpet is wool and called taupe. I think it works well. I think any of the 3 samples would look equally good. Darker will show every speck of lint though. I will now try and put a photo on. Forgive me if it doesn't work, for being a technophobe, and forgive me if it does for a messy house. I am going to clean today. Honest.

I can only speak from experience of tiles and Karndean. We have two dogs, live in the country, we and the dogs are in and out all day. The dogs both used to slip even on terracotta ( back in the old days), and, i'd be worried about shiny tiles, especially with larger dogs that could slip far more easily and cause themselves damage. The tiles were dark and had to go, as they showed up the dirt. The grout was the biggest problem, as it was easily stained, and just not practical with dogs. We swapped to Karndean around 5/6 years ago and haven't looked back since. It's simply the best, unscratchable, hard wearing, versatile, easily cleaned surface ever. We live in an old cottage and it had to fit in, so we went with Van Gogh, a floorboard effect look, complete with etched woodworm holes! Love it.

Composite Deck? Once down you'll have very little maintenance for years. You could find a colour that matches your Ikea tiles too. Let me know if you need any assistance.

I'm guessing by the layout, and fireplaces that it's an old Victorian building. The only thing to remember with flats is that unless you are the sole Freeholder as well as the leaseholder, then you have to get permission from the Freeholder for just about anything internally with regards moving / knocking down walls. I would say, that the best thing to do would be to have a small archway from lounge ( bed 2 ) in to the kitchen diner. The next owner can easily re-instate the wall if they want 2 bedrooms back.....................obviously 2 beds is more valuable than 1. Moving the Kitchen to the bedroom is a better idea and should be achievable as there is clearly drain access out the back near the toilet. If you were to do that you end up with a great sized lounge / diner in the biggest room. You have to take the advice of a structural engineer though, due to it being a flat as you need to know what's structural. I personally nearly always run things past a local estate agent to confirm that my changes are going to add value. I would imagine that a large / spacious well layed out one bed is going to be similar in value to a cramped 2 bed.