Müller focused on direct observation rather than studio artifice. In works like Near the Carpet Bazaar, Cairo, he used broad washes and confident brushwork to record the textures of the Ottoman Empire. His sketches from his 1843 expedition to Lycia show a preference for honest architectural detail. Even when painting familiar subjects like The Bridge of Sighs, Venice, he avoided the romanticised haze common in nineteenth-century art. He preferred a crisp, sketch-like quality that preserved the energy of the original scene.

Modern collectors value the spontaneity in Müller's compositions. His work lacks the heavy sentimentality found in many Victorian paintings. Pieces like Study of a Man, Bust-Length, in Moorish Costume offer a direct encounter with his subjects. The earthy palette and clear light in Gezicht in Stapleton Wood, bij Bristol suit contemporary interiors. His prints provide a sense of historical travel without the clutter of excessive detail.