One of those boulders, the one coming diagonally into the foreground, might make a nice foundation for a rock garden, which might also serve to delineate different areas of the yard (e.g. herb garden and children's playground).
In the soft part, I would put a few - maybe three - tall, narrow conifers like these
with several different interesting variegated and/or flowering shrubs in between.
These could be pruned at or just above the level of the railing, so as not to obstruct your view.
At the barbeque end, some hostas, rhubarb or yucca.
That's all low-maintenance, long lasting plant life that looks both attractive and interesting. (Have your ever seen a rhubarb bloom? Brief, but spectacular.)
If you wanted to get fancier, a few containers with annual climbing plants on the deck itself, or trailing plants in long boxes on the railing, would look very nice.
PS I don't know your climate; guessing Zone 5-6?
It's helpful to put your location in your profile.