I like the different sizes/shapes of retaining wall blocks. Also I really like the larger flatter blocks on top. Something about this height for the corner planter and maybe only 2 layers high for along the back fence.
This newly built home sits overlooking a lake, requiring several tumbled retaining walls and natural stone staircases. Also incorporated in the project was a paver patio for entertaining and a firepit overlooking the lake. - Flower Beds and Gardens
How to build a cheap garden rock wall or a simple concrete reinforced retaining wall. If you do not have much money and can't easily fix stuff you probably can still build these simple retaining walls.