Dreams or visions about a lily tell you about victory over the past, the female sexual organ and the fertile opportunities that come from it. Dreams about lilies also tell you about (sexual) sensual feminine energy and desires, overcoming and rebirth.
Another explanation is experiencing the end, mourning, death (death and rebirth) or grief and illness. An addition to this is setback, but also the loss of deceased loved ones. This is because the lily is widely used in death and funerals.
Picking a lily in your dream or vision also tells you that you have harvested and now you can reap the fruits, your fruitful ideas come true. Another explanation is that your sexual (sensual female) desires need attention.
Yet another explanation is that your problems are coming to an end, you are processing your loss, the emotions are being expressed. To see a lily in your dream or vision tells you that your desires, dreams and ideas are still beyond your reach, so you may need to set yourself different goals.