His work often features a smooth finish and a clear sense of volume. In pieces like *Portret van Jan Pietersz. Zomer* or his portrait of the flower painter Jan van Huysum, Boonen avoids excessive ornamentation. He focuses on the character of the sitter through precise facial features and subtle textures in clothing. His use of the oval format, seen in his *Zelfportret*, was a popular choice for domestic spaces in the late seventeenth century.

Modern collectors value these portraits for their technical clarity and historical presence. The paintings offer a direct connection to the Dutch Golden Age and the transition into the eighteenth century. Because Boonen avoided overly theatrical styles, his portraits maintain a calm and balanced appearance. They provide a sense of historical continuity without adding visual clutter to a room. The muted colour palette makes these prints easy to integrate into various interior designs.