Someone asked: before falling asleep, do I need to meditate while picturing the Buddha image sitting upright, the same way I would during formal sitting?

That isn't strictly necessary — choose whichever approach is easiest. All we really need is for the "knowing" — mindfulness itself — to arise, so that we remain aware and don't drift into forgetfulness. Pick whatever feels simplest and most comfortable, because if the method is too difficult and fights against how we naturally feel, we'll only manage it briefly before giving up. Approach it the way you'd approach something playful and fun — whichever version feels enjoyable enough to keep doing, use that one.

When we sit in meditation and mindfulness — a mental factor of the wholesome — arises together with wholesomeness, the Triple Gem appears shining at the center of our being, and we in turn appear shining at the center of Nibbāna. That said, not every being residing within Nibbāna shines this way. Only those beings who stand in universal goodness — who dwell within the wholesome system — have merit flowing through them, and it's that flowing current of merit which makes them shine. The wholesome system then continues refining and purifying their elements further and further.