A huge Milestone and mocking up backdrops

My original goal when I started this layout was to have the major infrastructure - benchwork, track, and wiring with basic scenery. I'm pleased to report that this afternoon, approximately 18 months after starting construction on the layout, all the track and wiring are completed well ahead of schedule. 
I've even gotten a start at roughing in the scenery, especially in the Enosburg Falls area around the implement dealer (come on, you didn't think I'd have a blog post without mentioning the implement dealer, did you?!)
One thing I've been thinking about before starting the around the walls scenery is the backdrop. One possibility I'm looking at is using Trackside Scenery's (for their website, click HERE) line of photo backdrops. 
I even mocked up a couple of possible arrangements. 
Trackside Scenery offers a varied and versatile line of backdrops, and the quality of the images is second to none. 
Unfortunately, they have a limited selection of fall backdrops, and the ones they do have are very - uh "vivid" - neat but as this test shows, so much fall backdrop might be a bit overwhelming on a relatively large layout. And since there's only a "Fall Valley" series (in the center of the image below) and a Fall Mountain series, I think the backdrop may end up just a bit repetitive. I don't know a lot about backdrops but I do know you (1) don't want them to be obviously repetitive and (2) they should complement, and not distract from the 3d modeling. 

For my second attempt I used backdrops from two different sets the Hickory Hollow and Valley Flats series - both of these are in the "green season." 
Frankly, I'm seriously considering doing the layout's scenery in the green season - for variety if nothing else. All, and I mean, all of my layouts since I was a teenager have had falls trees. Maybe it's time for a change of pace?
To that end, I even tried painting a couple of my fall colored Super trees with an overcoat of green paint. I'm happy to report that works, and actually adds another layer of color to the tree that makes it look pretty realistic. In fact, if I stick with the autumn trees I'd likely give each one a misting with the airbrush before installing them. 
But let's return to the backdrop:

Frankly, I think the profile of the distant landscape looks much better than with the autumn backdrop. 
I also like how the fascia (and the underpinnings of the layout) are all the same bluish green color. 
What I don't like about either of these is the obvious point where the top of the "sky" ends and the sky blue wall color begins. 
There's something like 2 feet of additional light blue wall up there - and it doesn't look natural. 
One solution would be to trim the backdrops at the treeline - and eliminate the photo sky. Frankly, I think that border between the photo backdrop and the wall can be as difficult to get right as painting the whole backdrop in the first place. 
A possible solution would be to simply paint the band of blue above the sky to match the fascia - creating an upper valence with paint. 
Photoshop makes it easy to rough this in, just to see how it would look. Forgive my rough photoshop skills, but I did this in literally 5 minutes before dinner. 

I wasn't sure I'd even like this, but frankly I think it sets the layout off better than running the blue up to the ceiling. 
I still haven't made a final decision on the backdrop, but I do really like the darker color defining the upper limits of the sky.