Lovely raised bed, and I agree the spruce will soon be too large. I suggest a small grafted Japanese maple or a very skinny, upright evergreen such as Ilex 'Sky Pencil'. There is also a coral bark maple with yellow foliage that might fit if you prune every couple of years. Coral bark maples are one of the few trees that can handle some pruning and still retain a great shape. This depends on where you live however. Japanese maples do best in mild climates. Evergreens are hardier if you live in a cold winter climate with temps that hit below zero degrees. Keep growing, Marianne Binetti