You might try some decorative plant stands if you want them to get tall. Certain types of coleus get about four feet tall with long arching flowers but, that's with a little bit of sun. Impatiens are a good ( spectacular ) choice for free flowering shade plants. Pulmonaria/lungwort, torennia, browallia are all great choices. I'll put in a helpful link for you.

Here is a link that might be useful: Shade loving flowers. Both, tall and stout.

Good sugestion about putting in plant stands! Shrubs might be out of the question? might puncture underneath side maybe? How about goats beard? that could hit the 3-4' mark.

Planting one or two tall growing shade trees into your landscape can help to cool the house reducing energy costs and also creates a beautiful place to sit and relax.
Blue Corydalis is a slow growing, evergreen perennial that will eventually form a dense 18" clump of elegant, 12" tall, lace-like green foliage.

All I can think of that is tall is foxglove and hydrangeas. Both do well in shade and add some color. If you plant both, the foxglove will be done by the time the hydrangeas bloom.
Remember that the foxglove blooms every second year so you want to plant a mature (ready to bloom) crop every year for two years so you have bloom every year.

I would try a shrub like a hydrangea, deutzia, neillia, or viburnum. Unfortunately, I think the list of tall, flowering, shade plants is going to be quite short.