Is there any achievement that gives out rewards?
Yes, there are achievements that reward you with shapes, patterns, sigils and accents (images that appears on your banner).
Here is an example: The Art of Conversation achievement.
Or this one: Slice of Life achievement.
You can tell if an achievement has a reward with just a glance in the achievement window. The small star icon indicates the number of rewards the achievement has.
In the example below, the Scavenger achievement has 6 rewards because there are 8 levels of the achievement. All but the first and seventh level have rewards.
