FileZilla 3 Icon set specification
Introduction
This document describes the requirements for icon sets in FileZilla 3.
  Please remember that if you want to create an icon set for FileZilla,
  that you should be available to update the icon set in the future when
  additional icon are added to the requirements. Otherwise the default icons
  will be used for the missing icons and eventually your theme will be removed
  once it becomes too outdated.
Requirements
  Since FileZilla is Free Software, the same has to apply to all artwork used
  in FileZilla. This means that all artwork has to be published under the GPL
  or a GPL compatible license.
  Note that the Creative Commons Attribution license is
  not compatible
  with the GPL.
  Each icon set should follow a theme, the icons should match nicely. Also,
  the function of the icon has to be easily recognizable.
  You should combine use of both color and shape. The icons are usually 
  displayed on a light background, though as we have no control
  over the background, all icons must also be recognizable on dark backgrounds
  or oddly coloured backgrounds. Avoid monochromatic icons.
Icon sizes
  All icons must exist in scalable form to accomodate modern high-DPI
  displays.
  The minimum size at which an icon can be displayed is 16x16 pixels. It is
  important, that the icons are good-looking at small sizes. Especially the
  smallest icon size should not look blurred beyond recognition. To improve
  visibily at these low sizes you can include icons in pre-rasterized form.
The most commonly used small icon sizes are:
  - 16x16
- 20x20
- 24x24
- 32x32
- 32x32
- 48x48
Color depth
  Regarding the used color-depth there is no limitation.
File formats
  All icons have to be submitted in the Scalable Vector Graphics (SVG) format
  and placed into a subdirectory named "scalable".
  As file format for optional fixed-size icons supplementing the scalable
  versions, the Portable Network Graphics (PNG) format has to be used. For
  each provided size there has to be a subdirectory with the size as name
  ("16x16" for example) containing all icons in the corresponding size.
Required icons
  The following icons together with the required file name are required in all
  icon sets for FileZilla:
General toolbar:
  - sitemanager - Sitemanager
- localtreeview, remotetreeview, logview, queueview
    - Togglebuttons for the local directory tree, for the remote directory
      tree, the message log, and the transfer queue.
- refresh - a button to refresh directory listings
- 
    processqueue - a button that starts/stops processing of the Transfer Queue
  
- 
    cancel - cancels the current operation
  
- disconnect - Closes connection to the server
- reconnect - Reconnects to the most recently used server
- help - a help button
Browsing toolbar:
  - 
    synchronize - Synchronized directory browsing: If user changes the local
    directory, the remote directory changes as well, and vice-versa
  
- 
    synctransfer - Synchronize contents of two directories: Transfer files
    from the source directory missing in the target directory, delete files
    from the target directory not existing in the source directory
  
- 
    compare - Compare local and remote directories: File entries in the
    file lists will receive a coloured background if they exist either only on
    the local or remote side, or when the file attributes differ.
  
- showhidden - show hidden files
- 
    filter - filter directory listings to remove unwanted files. Note about
    metaphors: Funnels are not filters, don't use a funnel metaphor.
  
- find - search for files
Transfer settings toolbar:
  - speedlimits - Button to enable speed limits
Context menus
  - upload - Upload selected local files
- uploadadd - Add selected local files to queue for later upload
- download - Download selected remote files
- downloadadd - Add selected remote files to queue for later download
Other generic icons:
  - 
    ascii, auto, binary - Transfermode icons for Ascii, binary
    and Auto mode.
  
- bookmarks - Bookmarks/Favourites
- bookmark - Individual Bookmark/Favourite
- folderup - "Go up one directory"
- folderback - "Go back to previous directory"
- file - icon for generic files
- folder - icon for open directory
- 
     folderclosed - icon for a closed directory, e.g. a collapsed directory
     tree icon
  
- lock - used in status bar to indicate encrypted connections
- server - server icon for the site entries in the Site Manager
- 
    symlink - overlay icon used in file lists to indicate that the displayed
    item represents a symbolic link. Note: It should only fills the lower-left
    quadrant of the icon