We propose the use of classifiers and machine learning techniques to extract useful information from data sets (e.g., images) to solve important problems in Image Processing and Computer Vision. We are interested in: two and multiclass image categorization, hidden messages detection, discrimination among natural and forged images, authentication, and multi-classification. Keywords-Machine Learning Techniques; Digital Forensics; Steganalysis; Feature Fusion; Classifier Fusion; Multi-class Classification; Image Categorization.