A little more info on the size of trees you would like, and perhaps a more detailed description of your yard i.e. 80 x 40 feet or something. How close to your house/patio/pool if any... and if possible, a picture would be great. Everyone here is awesome with advice the more you provide details.

When they built our house it was one of the first streets finished in our subdivision. We paid extra to get a larger lot with the ponding basin behind us so that no one will ever build there. However there is one two story house to the side behind the house where our bedroom is. When it was being built I went upstairs in it to see what their view of our house would be. Without leaning outside the windows they can see clear through my house into the living room and our bedroom with the curtains open. We went out and placed a coastal redwood in the yard so that in a few years they will not have such a view. I also got a type of blind that I can raise from the bottom so that we can still get some air at night with some privacy when the lights are out.

That probably is not a very constructive suggestion to you and it is going to be a very large tree, but I like my privacy.

Here's a picture of our backyard after we pulled out a dead hibiscus :( and white flowered potato vine. It's looking pretty bare! Over by the red plum tree we've got a little pond and a few koi fish. It's my favorite area of the yard; the rest of the yard is really lacking eye appeal!

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Do you want them in the planter areas? They look pretty slim... or do you want them in the lawn area (so the grass grows around it)?

That corner area (bottom pic right) in the lawn, looks great for a chinese elm (drake) or perhaps a Fraxinus (Ash tree).

If you want a tree in the planter, I would suggest bringing them out to be wider (losing some lawn). A carrotwood or perhaps a Golden Shower tree.. there are so many! Heck even a nice Citrus of some sort.

Think about the litter factor and the agression of the root system. You have block fence--a surface rooted tree could start cracking your fencing within just a few years. And many evergreen trees drop a constant hail of litter. Choose carefully.

A couple I like are:

Agonis flexuosa 'After Dark'. Lovely clean tree with a non-destructive root system.

Citrus make dense evergreen screen trees, plus they give you fruit.

Speaking of liquid amber trees, did anyone see that news magazine show (can't recall which one) about the couple whose home became virtually worthless because their aggressive liquid amber tree destroyed the slab foundation of their home? It also caused major cracks inside the house. Even after removing the tree, the roots lived on, growing like 80 feet away from where the trunk used to be. They have spent thousands and thousands of dollars, but they could not kill the roots. They are unable to sell the house, of course.

I have heard citrus trees are slow growers. When privacy is the purpose, who has ten years to wait?

You could layer the landscaping: plant a Cypress hedge against the wall, which will be a great screen. (there's a reason you see cypress all over the place!) Then in front of the cypress, plant trees that you really like. It would not matter if they are evergreen or not, because the cypress screen will provide the privacy.

Looking at your awesome green lawn, you have to consider if the tree or trees you select will get watered by your lawn sprinklers or not. Drought tolerant trees may not appreciate constant watering...

I have a mental block about only planting low or no maintainance trees that provide delicious fruit. Add in your climate and desire for evergreen and you have no choice but plant a Loquat tree! They prolificly bear golf ball size yellow citrussy flavored fruits usually in May and June. The one downside is the big seed cluster in the center which can be avoided by purchasing a named variety such as Gold Nugget or Big Jim. Check out crfg.org or rollingrivernursery.com for more info.

I would avoid Ash trees. They get huge, and you must weed out ash seedlings every year. Let me second Skrip's perspective: I believe your beds are far too skinny. As a matter of fact, I was thinking about posting on the "biggest garden mistake" thread that I wish I had created beds a minimum of ten feet wide. Mine are two to four feet wide: I am in the process of removing all of my flowering perennials to plant large shrubs and trees at the edges of the property. That means very little yard; but beautiful greenery on each side, privacy, and a only a small area that is thirsty, which allows for prettier flowers and grass.
An alternative to Italian Cypress that is also narrow and tall is golden bamboo, but you have to dig down two feet and install a "bamboo barrier" of heavy plastic to contain it. My neighbors have a back border of purple plum, white birch, and melaleuca (sp?) trees. It is spectacular because they have planted the trees in a wavy line that makes it appear that their garden goes on forever past the fence. They have Nandina domestica beneath the trees, which disguises the fence. It's pretty narrow: I would say that the whole thing does not extend more than six feet at the base of the nandina. The melaleuca is evergreen with whitish trunks that look quite woodsy mixed with the other trees.