I need a tree

You might consider a Japanese Acer (member of the maple family) that is slow growing and has beautiful maroon coloured variegated leaves. Properly planted, in the right conditions, these relatively slow growing trees would provide an attractive feature. They are deciduous so in winter it would look bare. For all year round leaves, how about a holly tree. Again they are slow growing but shape (and size) can be maintained. Also they'd make a good feature at Christmas time. With hollies, you have to watch as with some strains it is recommended you plant a male and female tree a distance apart to ensure that the female (I think) can be pollinated readily and bear berries.