The idea of topiary is horrifying to some people, but I think it has its merits, especially in small spaces!
Cloud trees in particular, can make a bare wall into a evergreen feature, and other seasonal or bedding plants and bulbs can be underplanted around it for year round colour.
The are reasonably easy to maintain if you purchase a pre-grown one, just trim as needed while keeping the shape. For smaller leaved ones use scissors, and gently clip away. Always take a step back to look every few snips to make sure it doesn’t get lopsided! Never prune anything if its going freeze outside.
The two cone shaped ones are lemon scented, and nice addition to the garden all year round.