well for the garden, you'll have to wait till spring but, put some tall plants/flowers near the building and smaller ones near the street. Ex:lots of lilies(orange and yellow) near the building, then candytuft in the middle of the garden and finally some Thymus lanuginosus near the street.

you are thinking about the space right now. it looks odd, no doubt. 1) when you fill in with the furniture, just make sure the three steps are hidden. 2) consider three potted plants of different height, so the rectangle is complete. 3) glass bowl with Siamese fighting fish for each step 4) figurines of different heights 5) 2inch square wooden bar on each step up to the top of the rectangle. and complete the entire rectangle if you want with a smaller rectangle open in the center my suggestion is, there is a reason why this space ended up like this. it will look great once you put something there. things like these are what make your house unique.

Adding a nice wall art would bring the room to life. Depending your liking either a collage of photographs or a single big photograph art or even a wall paper to the white wall. Check www.dahuez.com or www.facebook.com/dahuez

It depends on the function of the staircase and the building typology. For public building, it's 6 inches. For residential it is 6.5-6.75 inches. For residential interior ones it can be 7 inches. For terrace-to-tank like applications, it can be 7.5-8 inches.