Board Thread:Support Requests - Getting Started/@comment-1883569-20130502090247/@comment-452-20130502201216

It's not possible to export or import them all at once, unfortunately. But there are some shortcuts.

You can access a list of all files on a wiki using Special:ListFiles - the "(file)" link is a direct image link.

You can upload 10 files at a time using Special:MultipleUpload. (20 on some wikis, I'm not sure why)

I believe it should also be possible to configure a bot to do at least the second part automatically, but I don't have first-hand experience with this.

Remember that even if it's not always legally required, it's still nice to cite the source of any images you upload.