As a growing number of research groups exploit photoacoustic imaging (PAI), there is an increasing need to establish common standards for photoacoustic data and images in order to facilitate open access, use, and exchange of data between different groups. As part of a working group within the International Photoacoustic Standardisation Consortium (IPASC), we established a minimal list of metadata parameters necessary to ensure inter-group interpretability of image datasets. To this end, we propose that photoacoustic images should at least contain metadata information regarding acquisition wavelengths, pulse-to-pulse laser energy, and information regarding transducer design and illumination geometry. We also suggest recommendations for a standardized data format for both raw time series data as well as processed photoacoustic image data. Specifically, we recommend to use HDF5 as the standard data format for raw time series data, because it is a widely used open and scalable format that enables fast access times. To support long-term clinical translation of photoacoustics we propose to extend DICOM, the prevailing standardized medical image format, to officially support PA images. An international data format standard for photoacoustics will be an important first step towards accelerated system development by facilitating inter-group data exchange and inter-device performance comparison. This effort will thus form a foundation to integrate basic research with clinical translation of PAI.