the trick is that things that things that are firther away from you get smaller and smaller and things that get closer and closer to you get bigger and bigger as for moons adding the dark side (the shadow) can make it less 2 dimentional and look more realistic but the bigger and smaller trick can work with most if not all things when it comes to drawing. it creates a sort of optical ilusion and tricks your brain into thinking its closer or further away. first I drew it with the drawing upright then I turned the drawing upside down and drew the owl and moon in the corner so your actualy looking at the drawing upside down but its meant to be that way so that your looking doen from the top of the staircase with the owl nearby
this is what it looks like the other way up. now your looking upwards up the stairs next to the owl rather than looking from the top of the staircase. when the drawing is upside down- the right side up. the floor forms a platform so that your looking down the stairs next to the tawny owl