Radiated fields in the far-field zone of a small, thin-wire, square loop placed centrally above a finite image plane are analyzed by a set of 3D electromagnetic (EM) simulations. The impact of a finite image plane on the maximum radiated fields and on the shape of the radiation pattern is addressed. The image theory is extended to include the modelling of finite image planes by modifying the contribution of the image loop to the total radiated fields as a function of two parameters - the size of the plane and the distance between the loop and the plane. The proposed analytic solution provides a fast and simple method to calculate radiated fields in the far-field zone of electrically small, magnetically driven sources above a finite image plane.