If I understand the seasons in India correctly, you have already been through the rainy season. Don't wait until the next rainy season to get the problem with your drainage fixed. Now will probably be the ideal time to get it fixed. Please get someone who will tell you what to do and then have the work done. The paint on that wall in your beautiful home will keep coming off!

I agree with divadeva. More lights. If you can add pot lights do it. If they're already there add task lighting and up the wattage on the bulbs on the pot lights (replace with LED and you can make them brighter because the wattage on LED is lower for brighter light). If you have all of that add decorative lighting. If ventilation is an issue find a way to move the air around or add air filtration. Maybe the HVAC is deficient. Maybe you can add a HEPA filter instead of the standard one that comes with the unit. Call an HVAC specialist to see if there is a way to boost air flow in the room.

actually, to brighten up this dark and small feeling space, i'd look for a creamy base colored stone like khasmir gold or ivory gold, being sure to add an overhang on the island (if you like movement in the stone check out juprana granite) then exchange the pot rack over the island with either a pair of great pendants or a statement chandelier. from my own kitchen remodel experience i'll share you with you this: you'll get a much better price from a granite company then you will from a large home store ;) and be sure to take a cabinet door with you to shop. you can continue the granite onto the wall as a backsplash...they can cut the stone and make it go higher up the wall than the standard 3 inches which can be a great look. but if you really want tile, go for something simple that won't compete with the granite....like a cream colored subway tile. you can apply thim in a running brick pattern or a more modern stacked geometric pattern or even a herringbone. to control staining from food prep, don't use a white grout, use a slightly darker grout color that is inspired from the stone countertop. just remember that using a pattern on the countertop and another pattern on the backsplash can easily become overwhelming and then neither element stands out as the focal point. if you are spending a lot on a granite countertop, do everything you can to make it stand out as the best feature.

I have some suggestions if you are thinking budget friendly changes. Make a photo gallery with different size frames and arrange them parallel to the stairs, so you can enjoy each photo as you climb up. And for the area that will be on a level with your upper floor, try some pretty decal that will connect the photo gallery to upper level. And last, if you have budget add some beautiful hanging lights in the stairwell. Also think about repositioning your refrigerator.