It will help us a lot if you could let us know where you are, please? Fill in your profile with your city/state/country and then it will appear in all your posts. Just a zone really doesn't tell us anything except how cold it gets on average in winter. Summer heat, humidity, does it rain? the strength of the sun and day lengths all determine what will be successful for you. Also some info about your soil would help as well - is it sandy, clay or loamy? Have you had a soil test done?
Which direction does the front of your house face? This will impact what you can plant quite a lot.
You say you want an "all-season" garden but in zone 6a you will have winters that freeze so do you really want to plant all evergreens? The little Alberta spruce trees you have there are extremely slow growing, so you can't depend on them to make much of a statement for several more years. But you don't want to crowd or shade them out either.
There are some shrubs that stay fairly small, like red twig dogwoods. They come in beautifully variegated foliage, and when they lose their leaves in winter, their stems turn bright red, which can be really nice looking. Would something like that interest you?
Red Twig Dogwood (Cornus alba 'Elegantissima')
