I am not surprised that the Boxwood died. A west sun condition against a wall is a VERY hot exposure.
You didn't mention how high or long the wall is, but here are some suggestions that will do well. Just make sure they are watered correctly and check your plant zone ant that of the plants.
1. Japanese Holly 'Morris Dwarf' (wide, but not too tall). It can grow up to 4'H by about 7'W. This is an evergreen shrub, so for color you might consider adding perennials in front of the shrubs. Lavender 'Hidcote' or Nepata 'Walker's Low' are good ones.
2. Red Barberry 'Crimson Pygmy' - about 3'H. Red leaves. Depending on where you live (don't know), it might be semi-deciduous (lose some or most of its leaves in the winter).
3. Wintergreen Barberry - 4' to 6'H. Nice fall color.
4. For a deciduous plant, consider Weigela 'Minuet'. This shrub gets to be about 2' to 3'H and produces beautiful flowers in the spring.
5. For a really floral look, consider roses. Carefree Delight, Carefree Wonder, and Knockout roses are low maintenance.
If you have deer, and unless you want to spray for them, do not use roses or Japanese Holly.
