This article argues that thumbnail images are infrastructural images that raise issues of uncertainty in two distinct, but interrelated, areas: a legal question of how to define, understand and govern visual information infrastructures, in particular image search systems in epistemological and strategic terms; and a cultural question of how human–computer interaction design works with navigational uncertainty, both as an experience to be managed and a resource to be exploited. This paper considers two copyright infringement cases that involved search engines as defendants, Kelly v. Arriba Soft (2003) and Perfect 10, Inc. v. Amazon.com, Inc. and A9.com Inc. and Google Inc (2007). The cases are revealing of the issues that arise when thinking about thumbnails as infrastructural images in relation to uncertainty. Legal research on thumbnail images has focused on fitting them into the framework of copyright—which precedes digital technology. This article revolves around the infrastructuration of thumbnail images in a medial sense: as infrastructures of logistics and desire. The article draws on infrastructure studies, feminist visual and human computer interaction (HCI) theory and legal theory to examine how the thumbnail has been negotiated in legal terms, its cultural infrastructures, and the information behaviours they are designed to produce.