Image datasets are supported in OpenML as a workaround by using a CSV file with image paths. This is not ideal and might eventually be replaced by something else. At the moment, the focus is on tabular data.
OpenML-Tensorflow API currently only supports runs on image datasets. Other modalities will be included in the future.
Many features (like custom metrics, models etc) are still dependant on the OpenML Python API, which is in the middle of a major rewrite. Until that is complete, this package will not be able to provide all the features it aims to.