Diorama of toy spaceships on the wall or the ceiling, how do you install it?

I would suggest leaving the landing light on, but then noticed that you were in the basement and that messed up my initial thought! Sorry.

I’d get them as close to the wall or ceiling as you can without ruining the visual effect. (Is it too late to use forced perspective, w/ larger scale for foreground than background?) Then I’d rigidly attach them.

You could use speaker support brackets along the lines of this product. Or maybe just use long screws driven into screw anchors in the drywall of the wall or ceiling, though you’ll have to improvise the attachment points using small hardware or cement.

[edit] I thought of something else: Use wire coathanger stock to make several V-shaped or U-shaped brackets. Anchor both ends of each bracket in drywall by pre-drilling a slightly smaller holes. Several of these should prove rigid yet nearly invisible.

With an image of space as the backdrop on the wall, @gasman‘s idea could yield a a really spectacular looking artwork.