Ideally you would have a fence or hedge behind, with evergreen shrubs on the ends, deciduous shrubs between these and the flowers. Bulbs and annuals would be used to extend interest of main (herbacous) portion, which is on a sort of stage made up from previously listed elements.

Deciduous shrubs don't provide that much structure, more than herbacous plants but quite a bit less than evergreen shrubs. If your layout is more of an alpine garden (2 feet wide is a pretty small shrub) than the mixed border described above, maybe some of the many dwarf or even miniature forms of conifers would be suitable. Or, if you must have deciduous some of the compact, colored leaf forms of Spiraea japonica are very bright in spring. Long-blooming Potentilla fruticosa is also popular and available in small cultivars, although like the spiraea looks pretty grim in winter--and being a rose family shrub some kinds have foliage disease problems in some climates.

There are many evergreen azaleas that will stay in the 2-3' range. Azalea Girard 'Crimson' comes to mind...has beautiful fall/winter foliage. I know you said you don't like grasses but Blue Oat Grass stays a managable size & is evergreen (blue-green foliage). The spikey blades add a nice complimentary texture as well, IMO. Budleia davidii (butterfly bushes) can also be used as winter structure since they aren't pruned down until spring. A nice evergreen edger for a perennial bed is the herb germander. It can be pruned into a mini-hedge as a border. There are also numerous dwarf pine/spruce varieties that could be utilized.

I always design my perennials beds with 1-3 shrubs/trees as anchors.

Variegated Dogwood. youÂll have Bright RED Branches all Winter Long

I cannot say how it would perform in your zone, but I have a dwarf Nandina that is beautiful in almost any season here. Some of the ground hugging Cotoneasters have interesting Winter patterns and flowers and berries in other seasons. I have 'Blue Star' juniper in my rock garden and it is quite spectacular all year. I am trying the Asarum 'Green Velvet' and have had the A. europeaum for years. The latter is shiney green most of the year. Arum italicum has beautiful winter leaves here. Also, I am impressed by the patterned leaves of the hardy Cyclamen, but, again, I am only speaking for my Zone 7 garden.