This datatype provides a folder picker to select folder from the actual umbraco installation. In this first version there is no restriction to the folders, but in thoughts are excluding folders from selection or so.
Installation: Just upload the dll to the bin folder, add a new datatype in the developer/datatypes section and choose TH.FolderPicker as RenderControl. Now you can select the base path from which the datatype will pick the folders. In the content section then the tree will be shown from the base path.
The output will be the path to the folder from the root of the website, i.e: "/images/galleries/eventxy"