The most innovative forms of public interest campaigns are characterized by the constant research of new visual strategies to affect the enunciatee, provoking a pathemic and esthesic reaction to stimulate engagement to the social cause. In social campaigns, the effectiveness of images is expected to be more incisive, more apparently incongruous, stratified, or oblique. On the visual level the strategy consists of enhancing the reflexive opacity more than the transparency of images by means of the ostensive display of a fictitious metadiscourse. In these cases the agency of images relies on enunciator's competence to manage the veridictory logics of secret and illusion aiming to affect the observer on a cognitive-epistemic, pragmatic and pathemic level. One of the most common tactics in social advertising is stickering, the practice of placing uncommon, often big and spectacular, images in unusual locations in urban territory, taken out of their usual context. In these cases, the effectiveness of the social campaigns is based on the complex relation between images and urban spaces, intended not merely as contexts but as stratified co-texts. Cities are plural texts, subject to continuous transformation and to manifold different readings and practices. In ambient marketing campaigns space is recognized, interpreted, and played with, starting from the tracking of a deep narrative logic, through actions of camouflage and trompe l'oeil: images are used to deceive the eye and catch the attention of passersby, who suddenly find themselves involved in a fictional experience. The paper analyses the agency of images used in some of the most impressive public interest campaigns, offering a perspective that intersects visual semiotics, spatial semiotics and a semiotics focused on everyday life common practices.