Fractal analysis for the characterization of complex structures is widely used in many fields. Among the fractal models, the fractional Brownian motion (fBm) is well suited for the characterization of images involving a varying range of gray levels. This chapter focuses on the use of the fBm for image analysis. Starting from the classical fBm of unique parameter H, different stochastic models are defined and discussed. The fractal anisotropy is considered and different methods emphasizing this property will be discussed. An application of these models to the field of biomedical imaging is also presented.