Nikhil, personally I think an entrance stairway like that is a great place to hang personal and family photos, but you don't need to limit it to that, anything can be mixed in that you like. Don't restrict yourself to frame size with a photo either, a small photo with a large mat around it and in a large frame can look really good and can draw the attention in a group of photos. A staircase is one place where more is good too, but getting the balance right is another thing. Search on this website for examples, you will find a lot and use them to get the feel of how to arrange and group your photos. Lay them out on the floor first to get the effect you want before trying to hang. [houzz=] [houzz=] [houzz=]

Depends on what effect overall you want -- hot tropical feel (oranges and reds) or a bit more toned down? You can take inspiration from pictures of gardens with lime green heuchera or sweet potato -- often paired with chocolatey purple, silvery greens and blues.

The furniture in the 1st one is typically seen in renders and that's what gives it away. Also the tree is not quite real. Other details like creases in the carpets/dhurries and the pattern of it.

Lostinwoods, Covering the holes should not be a problem with a small dab of painters putty. If you are lucky or have planned enough the frames may cover the area left behind by hanger or clock. IMO, you should use colored photos with white frames as the room seems a bit dark as described by you. You may need some focus lights for the frames. Have a look at some of these photos. Thanks, Nitin Cornerstone Designs, Bangalore.