I think what you're mostly lacking is scale. Unfortunately scale takes either time or money. :-) If you want any trees in front, I'd do that first - well, this fall, anyway. Shrubs would be a main consideration, too. Though do check and see how big they get and plant for their mature size! It'll take a few years for your plants to mature, but it's worth the wait. If it were me, I'd put something tall at that corner to soften that edge; maybe a juniper? Though that close to the house, I'd check and make sure their roots won't become a problem. Other than that a twining vine on a trellis might be a good choice.

Debhawks, the last photo posted should have been your first one. I didn't understand the "unbalanced" comment. Now, seeing a non-myopic view of the Birch, I see the conflict. I'm still OK with the groundcover portion of my earlier submission, but think the tree-form shrub should be a smaller version... something that would only get 8' ht. So not intended to be anything one would walk below. Some of my advice about it will seem to conflict with advice I give later, below. But this is an architectural "fix" situation... not a normal, straighforward landscape use. Not enough time to do now, but let me explore this later. It could possibly be something different, too. Do I need to preach about how the Birch should be limbed up?... to higher than what you think because the upper limbs will hang lower over time. If you do the minimum, it will be back in your face not that much later. I would create at least a 12' clear trunk to start...asap. It's always better to start shaping woody plants while they're very young, but starting late is better than not starting at all. I would limb up the crab asap, too. Worry only about the trunk structure & canopy elevation. The head of the tree will form no matter what height you put it at (within reason... we'll not consider the outside extreme limits; we're just talking about normal situations.) Develop a nice bouquet shape of trunks. Remove those that spread too widely outside of the imaginary "cone" shape. (I think 50 to 60 degree spread generally works well.) To my thinking, a canopy should never begin below a persons head (but I've stated an exception above.) That's the minimum--or it obstructs view--but higher than that is fine. Think how you prefer the ceilings in your house to be somewhat above your head, not scraping against your hair. It's the same with tree canopies. On a small tree like the crab, I'd give a light trim to the outside dome shape of the canopy just to bring it into greater uniformity... if you have the means. You really DO need a tree at the left of house to make it look finished and established. It's too vacant over there. A medium size flowering tree could be nice. I'd also consider side a large tree-form "shrub" (12' - 15' ht.) by the mailbox corner--with some underplanting-- to help reduce the airport look of the driveway. There are very few instances where suitable shrubs in the tree-form can be purchased. The overwhelming preponderance of landscape thinking is ruled by horticulture, not by design. The horticultural thinking has it that woody plants, for the most part, should be allowed to grow as nature dictates... with just a little tweaking here and there. There are notable exceptions, but they have occurred with few plants. In most of cases it is far better to create the tree-form that works for your particular situation using the plant that suits your needs. It's not hard. It takes a little time, but not much effort. I can elaborate later.

Does it have to be a shrub or tree? I was thinking that some of the groundcovers, like a low growing sedum that doesn't need mowing, might look beautiful and compete less for nutrients with the maple. Thymes (lemon thyme comes in a nice variegated form) would do OK in shade too, and contrast with the lawn nicely.

The bed line could be improved. Trees don't look well positioned close to, or right on the edge, of a bed. Move the line such that the tree is more central to the peninsula. I do not get why you are cutting a path through the length of the bed. A lawn is a path. There is no need for another path a mere 12" away, especially since it takes up a relatively huge amount of the bed. The walk seems stingy and lowers the prestige of the house. I would consider widening it either by replacing or adding to it. The bird bath location seems competitive to the entrance. I'd move it to another location. After the hydrangea grows, a single one will easily occupy the entire space below the window.