Nice job !

Very creative and fun to portray the artificiality of a theater set. The background source is inspired. I wish there were a greater feeling of depth, however.

First off, I would delete the big star painted onto the upper right corner of the backdrop. At the bottom prong of the moon, the big star above the prong should not be casting a shadow on the prong (as stars are always much farther away than the moon). The medium star below the bottom prong has a shadow that doesn't match the strength of that of the other stars I think the moon's shadow [why is bottom prong's shadow weaker than the shadow for the rest of the moon?] should be moved more southeast to make it seem clearly the foreground element the girl is pointing at.

The girl's meager shadow seems inconsistent with the shadows of all the other elements. I would make the lighthouse bigger (maybe by at least 100%?). And make the blue mountain the girl and lighthouse are standing on darker and crisper to seem more foreground.