I have a similar aggressive slope in my backyard (though yours looks steeper) and am planning to landscape it into terraced gardens. How high from your stone wall base to the start of those evergreens, and how long horizontally?

What's behind those evergreens? Does the hill slope down again on the other side or are you just on a lower level than that house in the background?

Some kind of terracing is good if only just to be able to maintain the area. I have trails of concrete blocks dug into the soil on my steep slope so I can work up there safely. The other thing to consider is the tree roots. If they are all throughout the soil it will be difficult to plant anything substantial, and the tree roots may suck all the moisture away from anything you plant. Not that it can't be done, but you have to allow for that in your choice of plants.

Slopes despite those difficulties are great planting spaces.

Thank you for the feedback. The pine trees and evergreens are at the top, so the main face of the slope does not have too many roots (as far as I can tell!) but I am not thinking of anything too substantial. there is a fence on the other side, and so I am just on a lower level than that house. The slope is about 15 feet up from the base to the evergreens and 40 feet wide.

jpc,
Blue rug junipers would grow great on that hill.
Your going to have to slow the flow of water down with something tho.
Rocks, terraces, some kind of obstruction.
Even daylillies would work.
If you can put some obstructions so that the plants would get some water, you can grow junipers, (the kind that is a ground cover), daylillies, ornamental grasses, some shrubs, really anything.
It would look nice.
Check the soil though. See if it is good soil or not.
If not, you may want to add some composted manure when you go to plant your plants.