A lot of people ask "should I watch the Madoka recap movies?" and my answer is always, you don't have to, but there are lots of little visual callbacks in Rebellion that you wouldn't know are references otherwise. Perhaps the best known one is from the opening credits, where Homura and Madoka are sitting in chairs in a field, and they end up brushing their faces affectionately up against each other, a gesture which is commonly referred by fans as "doing a Luminous" (after the name of the OP).
Thus, when Homura wakes up as a witch in Rebellion, she ends up in a nightmare version of this scene, which ends with Madoka dissolving into pink goo before Homura can catch her.
What shocked me the most about this dream-within-a-dream sequence on first watch is how jarring the transition is, especially in terms of color palette and music. We go from darkness as Homura dissolves into a witch to bright lights and relatively normality for a moment, before the surrealism kicks back in, and it's quite a ride if you're not expecting it.
The flowers here are white clover, by the way. I don't know if that's symbolically relevant at all, I just think it's neat. Even though this particular field is flat, and ringed by trees (probably on the school grounds?), there is also white clover in bloom on the hillside when Madoka and Homura have their first heart-to-heart. The soft gentle harp soundtrack is similar in both scenes, too.
White clover flowers are also briefly visible in the Rebellion OP when Homura and Madoka are running through the amusement park. I don't know if Shaft included it because it looked cool or if there's some deeper symbolic significance-- in Japan, Trifolium repens is known as shirotsumekusa (シロツメクサ) but it's a foreign plant, so IDK if it has the same cultural significance of good luck there.
Gong back to the chairs again: they also appear in the post-credits scene, this time at the flower field hill (although the flowers are gone). Just as before, Homura is on the right, leaning against Madoka, but Madoka is no longer there.
I don't think you need to know anything about the recap movies to understand these scenes from Rebellion, in the sense that their meaning is deducible from the context of the film. It's unclear if the relevant segment from the Luminous OP is even "canon" to the main story because under what circumstances and timeline would that even happen, but its inclusion in Rebellion suggests it was at least a fantasy/dream of Homura's even if it wasn't a true memory. But unlike the original series, the recap movies were made with Rebellion specifically in mind, and as a result, certain visual imagery in Rebellion is way less random than it initially appears.
Akiyuki Shinbo makes a fascinating comment in the Rebellion theatrical pamphlet about how he sees the original anime as a complete story, and Rebellion is a direct sequel to the recap movies, which I haven't been able to stop thinking about ever since. No matter how you feel about that idea, it's indisputable that the movies are an attempt to bridge the visual gap between the anime and Rebellion, and should be viewed with that in mind.
For various reasons, I prefer the original anime, but whenever I watch the recap movies, my reaction is always invariably "oh, damn it, so that's where that came from, huh".
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