Right there at the inside corner by the steps looks like a great place for a tall shrub... with lots of desirable features year-round. I don't know where you are (and therefore what is hardy), but I would suggest looking into Calycanthus 'Aphrodite' since it blooms all summer with fragrant red flowers, grows to 8', and should do well in a sunny place such as that looks like.
Certainly there are more ideas that would likely go well there also, such as a dwarf or weeping japanese maple that could take sun (laceleaf, variegation, new growth color, fall color, winter stem color, and/or etc are all possibilities). Are there themes you particularly like? (Variegation, leaf shapes, fragrance, evergreen, ???) Knowing where you live would help. These are just the ideas that came off the top of my head.
What a fun canvas to play with!