Is it mutar to arrange star stickers in the form of actual constellations (say, on a ceiling) or is that included in the prohibition of depicting celestial bodies?
Regarding the "prohibition of making celestial bodies", there is indeed a prohibition to draw stars or any of the heavenly objects, which includes constellations. While the stars in this case aren't protruding images, most of the poskim assume that flat images are still prohibited (see Tosfos Avoda Zara 43b, that the reason is because these images look flat to us when we look up at them in the sky. This is the psak of the Tur/Shulchan Aruch Y.D. 141:4 and the Shach there, and Kitzur Shulchan Aruch 168:1).
The Shach, however, believes that the prohibition of drawing or representing the constellations only refers to a representation of all 12 constellations together, though the Taz argues. However, it seems like even the Shach only allows drawing the shapes of the constellations without drawing the 'points' as stars, because after all, the Shach himself prohibits the drawing of stars.
Ve'in Lamo Michsol (vol. 2) writes that it is prohibited to hang up stars or the like even though someone else drew/made them. If so, there would certainly be a prohibition of putting them up in a way that makes it obvious that they're meant to represent a heavenly body. (Of course, there may be dispensations for educational purposes, etc.)
According to the translator of the Moznaim Mishneh Torah, the prohibition on "drawing planets and constellations" applies to figures that represent them in astrology (e.g. the ones accompanying some piyyutim in the back of the Artscroll machzor) and not astronomical charts.
Primary sources to follow in an edit.