Well there's a lot of different species you can work with here. I'd start with Arborvitae for year-round greenery. These tall, narrow, hardy trees can grow 14 or so feet high and only be 4 feet wide at the base. Other deciduous shrubs could include viburnums, spireas, pussy willow, weigelas, forsythia, dogwood, clethra, and lilac. Go to our Plant Encyclopedia on this website and do an Advanced Search. This should come up with a list for you.