I had an idea for this awhile back.

You could make it just voices, or maybe a vision like he has in TROS when he touches the helmet, since he says “show me”. But basically, the vision would revolve around three lines he hears.

Palpatine: If the Jedi are not all destroyed, it will be civil war without end.

Vader: Bring order to the galaxy.

Snoke: And fulfill your destiny!

If we do get a vision, Kylo could get glimpses of the chaos of the Clone Wars, the Galactic Civil War, etc. and then maybe glimpses of a future where Kylo brings “peace” and “order” to the galaxy. Shots of the First Order, Star Destroyers over planets, confronting/killing Luke, etc.

One big benefit is that it elaborates on Kylo’s motivations for turning to the dark side, which we never really get in TFA. He didn’t just turn to the dark side because he was a bad seed or something. He at least had a reason for turning, which he thought would help the galaxy. It also lines up well with Palpatine’s reveal in TROS.