We discuss entropy characteristics used in various research techniques for investigation of complex dynamical systems including symbolic ones. The dynamics of a system may be studied by analyzing the phase portrait of a system obtained as a digital image. Symbolic dynamics methods allow combining entropy of a given dynamical system with the entropy characteristics of its phase portrait. We apply methods of image analysis based on symbolic dynamics, Rényi entropy, fractal and multifractal characteristics to analyze high resolution images having a complex structure. We also describe the results of applications of described methods to images of biomedical preparations.