Somewhere on the back burner, they are working on flower bushes (yea verily, for it has been Announced). So I thought I would suggest a few plants that might really pep up some lots.
Butterfly Bush/Summer Lilac (big richly green bush with purple spiked flowers)
Longwood Blue (smaller bush with blue/purple flowers all over, see also here)
Rhododendron (or azalea) (gets absolutely covered in blossoms, can look like a snowbank)
Cinquefoil or Japanese Rose (lots of large-petaled brightly colored starburst blooms)
Crepe Myrtles (petite ones), rose bushes, hydrangea, periwinkle ground cover, decorative grasses (I have one at my house that is an about one foot high fountain of grass with purple ferny flowers sticking up in the center, but hanged if I remember what it's called) ... so many possibilities out there. To look good in Istaria, I imagine we'd want richly colored blooms, perhaps contrasting with dark green foliage, with visual footprints equal to or less than a tree planter, and planning footprints very small to let the plants snug up against buildings and each other. Maybe they could be carefully shaped, or maybe have sprawly shoots all over.
It would be nice if each bush came in a variety of color choices, too. Including black roses for certain morbid fiends .... [:D]
-Levity Merrel
PS This is not a Now Now Now suggestion, so please don't yell about all the more important things the devs can work on. This is only my input for when they eventually /do/ work on flowers for lots, if they ever do.