Here are a few of my favorite locations:
Fly N B Park (c470/Lucent area) - open field, tall grass, trails, lake, mountain view, footbridge, lots of tall trees/shade options - this is one of my very favorite spots because of the large variety in a small area
Example: Fly N B Park Example 1 - Summer
Example: Fly N B Park Example 2 - Fall
Highlands Ranch mansion (Broadway/HR Parkway area) - beautiful stone, lots of pillars and steps, open fields, great views of mountains, trails, small barn
South Valley Park (c470/Ken Caryl area) - great views of foothills and red rock formations, lake, trails - perfect when there's no leaves on trees anyway
Example: South Valley Park Example
Mt. Falcon Park - a little further but perfect if you want a mountain feel, with a great view of the mountains, pine trees and rocks/trails
Example: Mt. Falcon Example
Three Sister's Park (Evergreen) - even a little further than Mt. Falcon, but such great views and a gorgeous barn
Example: Three Sister's Park Example
Writers Vista Park (Mineral/Santa Fe area) - a meeting place for the Highline Canal trail - large trail with huge, gorgeous trees, a white bridge, view of mountains
Example: Writers Vista Park Example
Hudson Gardens (Santa Fe/Mineral area) - a place that literally has everything - flowers in summer, gorgeous color in fall - just have to stay away from weekend afternoons/evenings because of lots of weddings
Example: Hudson Gardens Example 1 - Summer
Example: Hudson Gardens Example 2 - Fall
Downtown Littleton - great for a more urban session - so many great textures on the old buildings and great alleys
Open Space off Santa Fe, right next to Seminary/Platte River
Open space behind Northridge Rec Center (c470/Broadway area) - trails, tall trees, footbridge, fallen log, large open field with great mountain views, waterfall
Example: Northridge Open Space Example
DeKoevend Park (University and Arapahoe) - open green field, thick tall trees, a creek with little islands to put feet in and walk in!, bridges
Cheese Ranch Park (University and Quebec) - trails, tall trees, lake, waterfall like area, a field, lots of lush, green variety in a small area
Hildebrand Ranch (just down the street from South Valley Park) - open space, mountain views, cool old white barn
Example: Hildebrand Ranch Example (winter)
Example: Hildebrand Ranch Example (last part of this session/the barn ones)
Columbine Open Space (just south of Castle Rock) - gorgeous foothills, red barn, stone house
Mathews Winters Park (located at C-470 and I-70) - lots of trees, rock formations and a great bridge and stream
Example: Mathews Winters Example
Ketring Park (right next to Littleton Historical Museum-Broadway/Arapahoe area) - open fields, paved trails, fallen log, large trees, large evergreens
Example: Ketring Park Example
Gallup Park (right across from Ketring) - lots of trees, paths, etc. Super cute and compact.
Silo Park (something a little more east) - I remember it was a great little spot, but don't have good examples from it
South Glen Mall or Aspen Grove Mall - this is fun if you want something a little more urban, perhaps incorporating some shop signs, the fountain or the interesting stone and brick on the buildings
Jackass Hill - epic great mountain view but not much variety
Clear Creek History Park in Golden (have never done a session here, but heard it's a fun spot)