A word on alphabet π={u, r, d, l} can be thought of as a description of a connected picture drawn on a square grid: each letter is associated with a unit move of a pen, u coding a move up, r, d and l coding moves to the right, down and to the left. We define the notion of superposition of two pictures f and g as the set of pictures obtained when one draws first f and then g with the sole constraint that the resulting picture must be connected. We show that superposition does not preserve regularity of classical chain-code picture languages, as defined by Maurer and al. [12]. On the other hand, we prove, using constructive methods, that regular descriptive ”branch-picture” languages, introduced by Gutbrod.