I really envy you your sweeping backyard. If it were me, I'd focus on some natural planting along the back that I could view from the deck. I'd muck around by the creek, cut down the tree of heavan (ailanthus) and plant red maple, pin oak, sycamore, basswood, hemlock, river birch, sweetgum, nyssa sylvatica (common name escapes me, maybe black gum?) and silver maple. Some lovely specimen trees to look at, many with interesting winter bark. Then I'd plant some understory flowering shrubs--native rhodies (the carolinia ones, can't remember exactly, they smell great), witch hazel, amelanchier, sweetbay magnolia, spicebush, viburnums, etc. Then underplant with some pretty spring bulbs. I'd be vigilant to keep the poison ivy at bay. wood chip it, etc. Then sit back on my porch with some lemonade and watch the birds at the feeder. Up by the deck I'd plant some persian lilacs for the heavanly fragrance. A little grove of japanese maples and japanese white pine because I think those trees are gorgeous to look at. Then a big apple tree. Someday I might put a brick patio at the bottom of the deck, with a pergola over it, with a climbing rose and wild clematis providing shade. My cousin has a similar back deck with a pergola, and the wild clematis does a good job of cascading over it. My reasoning for doing decorative trees and shrubs and a more natural landscape is once they get started, much less time spent fussing with them than perrenials.

My advice would be to go on Houzz and start some idea books to figure what your style is . Right now all you will get is dozens of ideas that will keep you more confused than ever. We need info to help with this.

you have a very lovely room. you may want to consider a Chesterfield style sofa in a grey. I would place the sofa across from the fireplace and then the two chairs looking out the window... not sure if you have enough room for two sofas. looks like you also need to place a kitchen table and chairs too. insay that because with the open area you have, it may start to look crowded. heres a grey chesterfield sofa with some ivory chairs to give you an idea of how it would look with your chairs.