Answer: Seven feet is the size of a medium shrub rather than a tree, so this is quite a small size range.
You might be able to grow one of the smaller cultivars of Japanese maple, although these too might need pruning after a time to maintain such a small size. This would work only if the soil is organic, humusy, acidic, and evenly moist yet well drained. If the soil is dry, or if there is a lot of reflected heat, this tree will not tolerate full hot sun all day long.
You might look at Pieris japonica also, this is a broadleafed evergreen shrub. Another possibility might be the so called blue hollies, these take pruning well and could be kept to the size you need. These would all appreciate similar conditions to the Japanese maple for best results.
Another possibility might be Nandina domestica. This is a semi-evergreen shrub and would stay in your size range without pruning. It is tolerant of heat, sun and average soil.
Your local professional nursery staff may have different suggestions based on a more detailed understanding of the growing conditions in your garden as well as your overall design goals. In the meantime I hope this gives you some ideas.
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