Have you asked on the Rocky Mountain Gardening Forum? (or are you in a different area?) My brother lives around 8000 ft in CO, and he really doesn't garden, but he does have a variety of native wildflowers, grasses, and several types of native evergreens. I know that there is a native rose in his area that I've never seen in bloom but has ornamental bright red hips that last for months and I would definitely grow in a garden. You may find that there are smaller versions of some of the native evergreens from your area, either at local nurseries or at specialty nurseries such as this one that includes a list of evergreens including dwarfs geared towards the mountain west. If there are any natural areas, botanical gardens, nurseries with demonstration gardens, or public parks in your area, take photos of plants you want to ID, both close details and the whole plant, and get them IDed on the Conifer Forum or the Name that Plant forum. If you have neighbors who have plants that appeal to you, ask if they know what they are or where they got them. You may find that there is some type of garden organization in your area that would have a wealth of local knowledge. I know of one gardener who grows many plants from seeds found along road verges.

You can also look online at nurseries geared towards mountain and extra hardy plants, you many find additional options. For instance, I know of High Country Roses which has an option to do an advanced search which includes zones and I know that there are other nurseries in places like CO and NM that sell plants geared toward the low water, high elevations of the mountain west of the US. If you are in another country, I don't know what if any nurseries might be available.

You may also get ideas from books from the library with an emphasis on mountain plants or blogs written by folks who garden in the mountain areas local to you such as https://frontrangewildones.wordpress.com/news/ or http://prairiebreak.blogspot.com/p/blog-page.html .