Here's what I see
I find that your set up (from the photo above) looks like it is hard to get into your back yard using the patio doors. The use of an awnings will free up space and give you shade when needed, adding large planter boxes like the photo brings in a little life, and a relaxing feeling to your retreat. (See photo below)
If you really want to spend more.... Here's an idea for your hot tub, but if you did this I would move the hot tub where that small patch of grass is. Freeing up your family room window, cause this will block all light going into the home and will take away your beautiful view of the pool. Also placing it on an angel would give it a nice view of pool at night
A flowing path like this to make your back yard appear like it has more... It could replace the small patch of grass winding behind that wood box to seem like you have more yard. Grow a climbing flowering vine around the box and maybe add a pergola to it. Turning the box into a structure rather then a utility box. Possibly even tying the pergola into the fence, making a partial covered flagstone pathway in and out of the yard. Plant lots of perennials to fill up all the grass area.
Adding a pergola like this at the back and side of pool will bring some privacy to your yard blocking out those window to the houses behind. It also can add some seating in your small garden
You already have a very very nice back yard and I'm not sure how much more you want to put into it. Just adding more shrubs and maybe a pergola for privacy is probably all that's needed... good luck, have fun and be sure to post photo's of the finished product for us all too see
