Examining the understudied collection of costume images from Heidelberg Calvinist, lawyer, and church councillor Marcus zum Lamm's (1544–1606) ‘treasury’ of images, the Thesaurus Picturarum, this article intervenes in the historiography on sixteenth-century German national imaginaries, emphasizing the import of costume books and manuscript alba for national self-fashioning. By bringing late sixteenth-century ethnographic costume image collections into scholarly discourse on the variegated ways of conceiving and visualizing Germany and Germanness over the century, this article sheds new light on a complex narrative of continuity and change in the history of German nationhood and identity. Using zum Lamm's images as a case-study, this article stresses the importance of incorporating costume image collections into a nexus of patriotic genres, including works of topographical-historical, natural philosophical, ethnographic, cartographic, cosmographic, and genealogical interest. Furthermore, it calls for historians working on sixteenth-century costume books and alba to look deeper into the meanings of such images and collections in the specific contexts of their production; networks of knowledge and material exchange; and – in the German context – the political landscape of territorialization, confessionalization, and dynastic ambition in the Holy Roman Empire between the Peace of Augsburg and the Thirty Years War (1555–1618).