Tree peony's have very eye-catching flowers and unusual seed pods that look like jesters hats but unfortunately they are faily slow growing and may take a few years to fill a gap completely, but I think the wait may be worthwhile and should reach about 5-6ft eventually.
the site needs to be sunny and sheltered. The double flowered varieties may need staking. Good Luck. Tbird+
they are really beautiful but no they are slow growers and can be a bit susceptible to frost. They can also take a while to establish themselves after moving
If you want something more unusual than a rose how about a tree lupin like regular lupins but growing as a bush