What is Banquo rewarded with by the king?

Not much! Just praise, and a warm hug.

In Act 1, Scene 4, it's clear that both Banquo and Macbeth have shown bravery in the conflict, and King Duncan readily acknowledges that. First, the king confers the honorable title and position of "Thane of Cawdor" on Macbeth. It's a major reward: it raises Macbeth up in status.

Next, the king addresses Banquo. We might expect a similar reward to be given to him, since the king says:

"Noble Banquo,
That hast no less deserved, nor must be known
No less to have done so..."

This means that Banquo deserves just as much as Macbeth, and everybody should know that. But then the king goes on to say:

"...let me infold thee

And hold thee to my heart."

In other words, "Come here, let me give you a warm hug." That might seem like a letdown, but Banquo is okay with it. He replies politely.

A moment later, King Duncan hints that Banquo might get a title of nobility, too:

"But signs of nobleness, like stars, shall shine

On all deservers."

However, we don't hear any more about it. Banquo seems honored just to be recognized and treated with warm kindness by the king. Because of this, you can see why he's Macbeth's opposite. Whereas Macbeth is greedy and ambitious, Banquo is selfless and content with what he already has in life.