My own child so far has not had much trouble with scary dreams or bedtime anxiety, but here are two ideas–one from my own childhood experience, one from my brother’s–that I’ve never seen in professional advice on getting nightmare-prone children to sleep:

I had a tendency to imagine things lurking in the dark.  Sometimes I got so frightened I couldn’t sleep, and sometimes when I did sleep I dreamed about those things “getting” me.  My parents quite logically provided a night-light to make my room less dark.  Still, I saw some sort of monster or mutant lurking in the shadows nearly every night.  This continued until I was twelve years old.  One night, I was about to drift off to sleep when I suddenly noticed that the folding doors of my closet formed an enormous, smirking face!  It looked like an unsympathetic giant with my bed balanced on his belly, waiting for me to relax so he could shovel me, bed and all, into his gaping maw.  I felt simultaneously terrified and ridiculous, because I knew it wasn’t real, but now that I had seen it I couldn’t stop seeing it.  I tried blocking it with various objects, but it just kept smirking, and I thought, “If only I didn’t have to look at it…” and that’s how I realized the night-light was the problem!  Not only did it enable me to see things in the room, but because it was a single light in a strange, low place, it cast weird shadows that distorted the appearance of innocuous things.  Getting rid of the night-light made my nights much more peaceful!

My brother had terrible trouble with monsters when he moved into his own room at six years old.  This is what worked for him: My dad gave him a gigantic rubber spider, about eight inches across with all kinds of fearsome details, and told him that this spider was our friend and ally but that monsters are just terrified of spiders and allergic to them too! My brother put the spider next to his pillow. Sure enough, it scared all the monsters away.  We eventually had to get a duplicate spider because my brother wanted to play with it during the day (it was the hero of everything) but misplacing it before bedtime was such a problem.  I can’t recall how long he kept the spider on his bed, but I know he was able to go away to college without his spider.  If a child is afraid of spiders, a dragon or some other type of fierce creature could perform this valuable service.