This collection contains datasets of curated images of maize seedlings from the BonnMu resource, a large Mutator transposon-tagged population developed for both forward and reverse genetics studies. The BonnMu population was generated by introducing an active Mutator transposon system into multiple maize inbred lines (B73, Mo17, Co125, F7, DK105, and EP1), creating insertional mutations throughout the genome. Flint and dent lines were mutagenized by crossing with a Mu-active line (Mu4 per se). Selfing (@) of the F1-plants generated F2-families segregating for recessive mutations in a 3:1 ratio. Therefore, the BonnMu F2-families comprise a genetic background of 50% inbred line (e.g. B73) and 50% a Mu-active line. For simplicity reasons the genetic background of the different BonnMu F2-families is referred to as B73, Co125, DK105, EP1, and F7, respectively. Between 2018 and 2026, seedlings from these F2 stocks were grown in a standardized paper-roll system and photographed at the seedling stage, 10 – 14 days after germination. In addition, visible mutant phenotypes were manually recorded. These phenotypes affect diverse aspects of seedling development, including root system architecture (e.g., altered root length), leaf traits (e.g., changes in color or morphology), and overall plant growth (e.g., dwarfism). The primary purpose of this dataset is to facilitate the discovery of mutant phenotypes in maize. Its unique value lies in the combination of a large-scale mutant population, standardized seedling images, and manually curated phenotype annotations. Users can browse the dataset to identify both well-known mutant classes, such as albino or pale-green seedlings, and previously unreported phenotypes, such as seedlings with dark red root systems. Each phenotype record is linked to the corresponding seedling image through a persistent DOI, enabling rapid visual inspection. To facilitate downstream functional genomics studies in maize, users can request seed stocks of interest from the BonnMu resource (bonnmu@uni-bonn.de), curated by the Marcon group at the University of Bonn.