I think a simpler solution would be more in line with the current Orchard admin tools. The media admin page already lets you select files and it already presents an "Actions" drop down list with an apply button. Today, the only listed Action is Delete. Simply
adding "Export to Zip" as an option would let an admin easily zip up any or all media files. The zip archive could simply be stored in the media folder itself and downloaded through the browser or accessed by URL. I'm proposing a simple extension
to the current Media admin page.
As a workaround for now, I told my content team to use
WGet and simply create a list of file names to download and then run Wget like:
wget -B http://orchardserver/Orchard/Media/Default/images/ -i exportlist.txt
to bring down all the images. Then zip them up on the PC and the files are ready to be copied to another server or backed up or archived or stored in source control along with text content exported through import/export module