I like to display a tree-like view of all files in an asset source:
I know that I can iterate over all assets in a source ({% for file in craft.assets.sourceId('1') %}) but this gives just an alphabetically sorted list of all files. Maybe we need something like the nav-tag.
Yoursort, my answer was based on the assumption that the AssetsService could be used in templates. Ofcourse, only the variables can be used.
I don't have time to dive into this (now), but I think your best bet is to get all images, use `asset.folder' for each asset and 'rebuild' the hierarchical list of folder and their assets. Again, use cache ;)
I have created the Assets Browser Plugin which allows to browse an asset source or a specific folder on the frontend.
Although it is not a treeview it serves me well for outputting a download area on the website. It works even with the Internal Assets Plugin for a member-only area.
