Not sure what grows well in your zone, but I would start by planting some type of flowering ornamental tree on the far left edge of the house. Don't plant it in front of the house, but rather to side so it frames that side of the house. Once your decide on what type tree/color you want you can then decide on plants to accompany it. Hostas are pretty easy to grow and they also propagate quickly so in two years you should be able to split them and plant half in other locations as well.

Not being familiar with what is winter hardy in your region, I hesitate to make a lot of specific recommendations. However, a few things to consider:

Japanese maples are adaptable, but have only moderate to low tolerance for salt, so think about whether your road is salted in winter and where run-off goes when you are placing that tree.

Basically, think about placing plants to connect your house to the land, so it looks like it is nestled into the setting rather than sitting atop it, and something to soften some of the edges. The large trees behind and alongside your home give you a good start on this.

Evergreens will, of course, give you color and coverage year 'round, but don't overlook deciduous plants hardy in your region that will also provide winter interest, like winterberry holly (you'd need a male and a female), red twig dogwood, witch hazel.

Plants native to your region are usually a good choice, as they are well-suited to the climate and have co-evolved with and support local wildlife (think birds, butterflies, bees, and a host of tiny beneficial insects that help control pest insects). Therefore, native plants usually (but not always) require less attention from you. There are many non-native plants, too, that will "play nicely" with your native choices.

Choose plants that are well-suited to the site where they will be living. Consider the amount of sun/shade, moisture levels, wind conditions, and, very important: your soil. Best bet is to have a soil sample analyzed for structure, pH (acid/alkaline balance) and nutrients. Here in the U.S. we have our cooperative extension services, run by state universities, with offices in most counties that provide a wealth of information, including soil testing. Perhaps you have something similar? If not, then you can do some basic tests at home. Most common landscape and garden plants on the east coast of North America prefer slightly acid to neutral soil that drains well, but is rich enough in organic matter to retain some moisture and nutrients.

Due to your long winters, I would probably focus on some evergreen shrubs for the front. You could add some flowering bulb plants for spring interest as well, and can then plant annual flowers in the summer for color once the spring flowers are finished blooming.

A nice flowering tree to the side of the house would be pretty. I'm not familiar with what type for your zone though. I lived in the Midwest and we had a lot of crab apple trees...a bit messy, but I thought they were lovely.

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If you decide to plant shrubs near the house keep in mind they will grow. A common mistake is planting too close to the house. Give them plenty of room.