A sourwood is supposed to have good fall color and it flowers, I'm not sure of its size or speed of growth. I had a Parrotia persica a long time ago and it also had beautiful color, again I don't know how fast it grows; but I do think it stays pretty small for a tree. Japanese maples which don't weep are very pretty and about the right size eventually even if they don't bloom. Weepers are pretty too, but basically shrubs, not what you're looking for. Fullmoon maple is one I lust after, but do not yet own; it is glorious in the fall at a local nursery. I do have a Katsura, and for me it is pretty slow growing; but I don't give it much supplemental water in the summer so that could be why. Mine's grown maybe a foot in two years.

You might also want to consider a gazebo or arbor, that would get you shade much more quickly than a tree.

Good luck

Both the sourwood and parrotia are quite slow growing. Japanese maples also grow very slowly but there are many lovely choices. A katsura (Cercidiphyllum japonicum, not the J. maple cultivar) could be a very nice choice. You can get a decent sized one for a relatively reasonable price, they have a moderately rapid growth rate and produce a modest shade canopy. They also have great fall color (and fragrance, too). They are pretty much problem free trees although not especially drought tolerant.

Katsura tree grows quite large. Try a vine maple.

I thought vine maples preferred shade, this sounds like a hot sunny position they'd hate.

I have a small strawberry katsura that is having a really hard time. Its leaves are delicate and it does not like direct sun or heat. It wants water and coolness and light shade while it's young.

Part of it depends on where in PNW poster is. In western WA vine maples are planted in all manner of situations, with some variation in results of course. Successful specimens in sunny locations fill in and make good screens. With large ones still being wild-collected locally, the much-desired instant screening is possible comparatively cheaply - nearly all other trees of comparable size seen with any frequency at retailers being nursery grown and much more expensive.

I suggest maybe something completely out of the ordinary and plant a couple persimmon trees. They are stunning in fall color, and green shiny leaves in the summer and gorgeous winter interest with fruit, at least before you harvest the orange orbs.

I have a wonderful Silk Tree, Albizia julibrissin that is most interesting and pretty. In one year the canopy is big enough for some shade and in three years it is quite dense and showy. Mine is underplanted with epimedium which is great because this tree drops a lot of leaves and flowers which can be hidden under the carpet of epimedium. The leaves fold themselves up at night time. It flowers continuously from July until frost. And in our climate is not invasive.

My grandparents had a silk tree, a very pretty thing--I have a weakness for delicate leaves.

Clerodendrum/harlequin glorybower? Has fabulous fragrant flowers and cool berries, can stay that size if given that size area. Fall leaves aren't its main thing--more the seed pods that come from the flowers, and the big luxurious leaves when they're in.

Grows fast, can be limbed up to sit under.

Maybe something for you here...

Here is a link that might be useful: Arthur Lee Jacobson - Trees That Merit Planting in Seattle

I like the 'Red Cascade' Mt Ash in my small patio courtyard. It looks exotic and is a fairly fast growing tree that stays small. Makes lots of pretty berries that birds devour in a day.

For a page on the Sorbus from its introducer...

Here is a link that might be useful: Red Cascade Mountain Ash

I suggest Golden Rain Tree, Koelreuteria paniculata. The leaves turn orange in the fall, and they have decorative seed pods.