You asked about rhododendrons. There are Northern Lights out there that might do quite well in that area. The one that comes to mind for you with the white trim on your home would be Rhododendron "White Lights". it's deciduous and would grow to somewhere around 4-5Ã¢â‚¬â„¢.
Hibiscus syriacus has become a weed down here. don't know that it would be a weed up by you or not though. I had received some in a plant exchange and have since destroyed them when they began re-seeding into a natural area on my property.
Japanese maples I sure do like a lot but have very little experience with them.
Convallaria majalis might do too well by you. That one is the European Lily of the Valley and it's documented as being an invasive species-
Since you have considerably more light, I think you might want to check out Rhus aromatica Ã¢â‚¬ËœGrow-LoÃ¢â‚¬â„¢. Neat plant that I have growing in full sun as well as in part sun and it's doing equally well in both locations. The size might lend itself to front spots in your bed. Some refer to it as a ground cover. Scratching my head at that one.
Buxus spp. (Boxwood) might be worth checking into for the area directly in front of your windows. They seem to be bombproof and tolerant of full sun to part sun. Many cultivars available and most have low growth habits and you can whack at them with wild abandon.
Another plant I think might be a great performer would be Ceanothus herbaceous. it's sold down here under the synonym of C. ovatus so look it up both ways. Height of about 2.5-3Ã¢â‚¬â„¢ on that one.
Backing up to viburnums a little bit, thereÃ¢â‚¬â„¢s a Ã¢â‚¬ËœChicago LustreÃ¢â‚¬â„¢ out there that might tickle your fancy. Nice height of only about 8Ã¢â‚¬â„¢ . There are too many viburnum cultivars to list and I really think a regular old Viburnum trilobum cultivar would do very well out front and most of those would be in the same height range of the Ã¢â‚¬ËœChicago LustreÃ¢â‚¬â„¢. I'm personally looking for Ã¢â‚¬ËœHahsÃ¢â‚¬â„¢ but I have 'Bailey Compact', Ã¢â‚¬ËœWentworthÃ¢â‚¬â„¢, and Ã¢â‚¬ËœAlfredoÃ¢â‚¬â„¢ here. All are exceptional plants.
Corylus americana is a plant I like to toss in whenever I can. It fruits at around 5-6 years and many species of birds love and depend upon the hazelnuts for survival. I like its delicate blossoms in spring.
Many shrubs can attain decent heights and can work like a tree in confined spaces. I am particularly fond of multi stem forms.
Epimediums I don't grow. Like the looks of them and think they are a good suggestion. I don't see them out and about so why not try a few? Experiment. If they get weedy for you, waste them. I can't see them doing that up that far north though.
I share MaineDesignerÃ¢â‚¬â„¢s substantial reservations regarding Lamium. Aside from that, it makes me itch and I get hives up my arms when I remove it. I'll plant Poison Ivy before I'd plant that. At least Poison Ivy benefits migrating birds. And yes, I leave a few Poison Ivy plants on my property specifically for the birds but I've got much more space than you and certainly am not suggesting you use that on your trellis.
Speaking of that trellis, I now believe you might be able to have luck with a Clematis.
Awww gee thanks MaineDesigner ;) Grasses, sedges, and rushes are by far my weakest area. I am familiar with quite a few that are indigenous to where I garden, some of the most common that are regional wetland species, and sort of so so with tall grass prairie grasses. I have been taught how to key them out and it just isnÃ¢â‚¬â„¢t sinking in for me. They really all start looking alike to me after a while. When I determine which species I want, I purchase them from reputable nurseries that I am counting on to have provided me with the proper plant. I have great success propagating grasses and sedges but after that I'd be doomed. Ferns I am fair to midland with. Have done some spore propagation with them and have used them on my property here. In order to make suggestions, I'd have to know if grasses even appeal to you or not and mind youÃ¢â‚¬Â¦ my suggestions will be very limited.
Spring ephemerals are always a great choice. What I like best about them is that you can plant other species to grow up through them to continue the show through the growing season.