Have you thought about about concrete for your sleeper wall?
As well as plain concrete it’s possible to have a wide variety of other finishes, and colours.
Here is an interesting ‘Stacked Stone’ appearance wall I saw the other week.
Some of the other options include ‘Exposed Aggregate’ and ‘Split Stone’ and even ‘Wood Grain’.
Just do a ‘GOOGLE Images‘ Search for “Concrete Sleeper Retaining Walls” and you should find a range of styles.
An advantage of concrete sleepers is they don’t rot, which means a quality lasting finish with no maintenance!
Prices start at around $25 for a 2.00m x 200mm panel, rising to $50 for some of the more attractive finishes.
See Retaining Walls for more information