An expression that identifies a picture by name, number, or id, using one of the following forms:

card.pictureID(posInteger)

card.picture(text)) // name

card.picture(posInteger) // number

background.pictureID(posInteger)

background.picture(text)) // name

background.picture(posInteger) // number

For example:

thisCard.pictureID(3)

thisCard.picture("Widget")

thisCard.picture(1)

thisBackground.picture(2)