In experimental settings, cognitive processes are influenced by characteristics of presented stimuli. Knowledge about stimulus features is important to manipulate or control the influence of stimuli. To date, there is a lack of standardized data incorporating such information for complex abstract stimuli. Thus, we provide norms for a database of 400 abstract and complex stimuli. Grey-scaled fractals were rated by 512 participants on the stimulus features of abstractness, animacy, verbalizability, complexity, familiarity, favorableness, and memorability. To establish external validation, we evaluated objective measures for selected stimulus features, including a) classification-confidence of a deep neuronal network labeling the fractals was negatively correlated with subjective ratings of abstractness and positively with verbalizability, b) data compression rate of fractal image files was positively correlated with the subjective rating of complexity, and c) performance in a recognition-memory task with a subset of 60 fractals was positively correlated with the subjective rating of memorability. The present work fills the gap of a standardized database for abstract stimuli and provides a database with valid norms for abstract and complex stimuli based on subjective ratings and objective measures. This database can be used to control and manipulate these stimulus features in experimental settings using abstract stimuli. Such a database is essential in experimental research using abstract stimuli for instance to control for verbal influence and strategy or to control for novelty and familiarity.