In fact he might like it a bit warmer on the warm end of the enclosure, say 85-88 F... however if he just ate, they prefer to sit on the heat continuously to help digestive processes (this is normal).
If the snake is continuously on the hot end, even when the food is digested, then likely the cool end is too cold or the hot end not hot enough (or both). If he's constantly on the cool end then the hot end may be too hot. Can also be that either end doesn't provide sufficient security for him to feel safe. Hard to say like this, a lot comes from observing the snake over a longer period of time
Your enclosure does look like providing sufficient hides, and you just fed him, so likely he's just digesting... if he remains there forever then likely it's a bit to cold for his liking.