Before you begin planting or purchasing anything, check and decide how much space you have along your corridor. Make sure the neighbours and their prams, backpacks and luggage can still pass through easily.
It is NOT recommended that you put anything on the parapets, so you can consider buying pot racks and holders to hang along the railings.
In our case, we upcycled the wooden slats from a discarded bed as well as used pallet wood to create shelving that was functional and looked nice (nothing a cheerful coat of paint can't improve).
Next, we discovered that the morning and evening sun were both very strong along our stretch of corridor. This meant we needed to select plants that were preferably more heat-tolerant and drought-tolerant. Succulents, basil or hibiscus for example, were a better idea than a peace lily.