Try this Houzz story for ideas misshayley [Get the expert lowdown on retaining walls[(https://www.houzz.com.au/magazine/get-the-expert-lowdown-on-retaining-walls-stsetivw-vs~32529705) and if she could incorporate some seating too that would be nice. Or planter boxes and seating...Good luck!

Orange brick looks good with beige https://www.houzz.com.au/photos/traditional-exterior-traditional-exterior-nashville-phvw-vp~6689812 with gray with green

we had custom made Corten Steel edging manufactured by a local steel fabricator......ours is curved from ground level up to 30cm tall around a round island bed and still looks gorgeous after three years ..

While I like the steel look I always wonder about heat transfer into the soil as I know this is a problem with colorbond raised beds. In summer the soil bakes the plants. Just fine if you have arid plantings but dire if you have a cottage garden. I have a similar dilemna on the north side of my garden. Would love corten but not if it's going to burn everything in the garden bed.