Testing photo, audio, and video uploads may require files of dozens or a few hundred megabytes; currently the docker image limits upload size via Special:Upload to 2 MiB. Should probably match the production setting of 100 MiB to simplify uploads of medium-sized files.
This is controlled with the php.ini settings upload_max_filesize and post_max_size, which are awkward to edit manually and cannot be set in LocalSettings.php.
(Larger files can be uploaded via CLI or using UploadWizard through the chunk stash.)