Candles are pleasing to the eye. Lighting them can make for a beautiful ritual and involve other mourners. This is a particularly good way of involving children.
You will need something to display candles on. A small table might do, but is likely to be a little low. A flower stand works well with a circular tray—a pizza tray—gaffer-taped to the top of it. You may have to improvise!
You could have a single candle in a candlestick surrounded by many nightlights. The central candle can symbolise love, the nightlights memories. At an early part of the ceremony, invite people to light them. At the end of the ceremony, after the farewell, they will still be burning, making the point that, though people die, love never dies and memories never die.
Some crematoria reckon candles to be a fire hazard. If yours does, demand to see their risk assessment and speak to the fire officer. The purpose of a risk assessment is to enable something to happen safely. Some crematoria allow it, so all ought to. You may need to negotiate with remorseless diplomacy. If they refuse you could use LED candles like these.
The right incense can create an ambience. Beautiful smells can evoke a sense of wonder and mystery. You can’t do this at a crematorium, though; the next people may not like it.