Most Helpful Guy
It's really nice to be honest as a first background, wish the island was centered and zoomed on a little, you could add some flying creatures and remove the yellow lights, overall it's still a wonderful work, keep on improving!
Most Helpful Girl
It's quite good in general. (I'm also an artist, though I don't focus on backgrounds)
I suggest maybe adding a luminosity effect to the parts of the drawing that are supposed to emanate light (I keep in mind as you said, the lighting is off).