Don't get him things for halls specifically, you could get some bits for his bedroom/desk that he can use at home- good keyboard, lamp, dust buster type hoover, stationery, rug etc. Neon lights go down well with that age.
Gadgets like a projector and screen for his bedroom, or a scent diffuser (oliver bonas have a good one IIRC).
What does he like? If he's a gamer then money/card for games, or headphone hanger, or comfy gaming chair.
If he'd outdoorsy then a good coat, binoculars, books on activities he likes (bushcraft, survival skills, wildlife spotting)
If he's into sports then team merch, sports equipment, tickets to events.
If he's musical- decent headphones, vinyl, tickets to gigs.