If you want to change the special folder icons (xdg user directories), you'll have to change them by making a custom theme. They are set to a specific name which is provided by the theme, and based on which folders are set as your Music, Documents, Videos, etc… folders.
To set a custom icon name to use from the theme, for the ~/.wine/drive_c
folder for example, you can run the following in a terminal:
gvfs-set-attribute ~/.wine/drive_c metadata::custom-icon-name folder-wine
This should make Nautilus use the folder-wine
icon. However, this icon will not be used in GTK+ file selectors or other applications. To unset the custom icon name, you can run the following in a terminal:
gvfs-set-attribute -t unset ~/.wine/drive_c metadata::custom-icon-name folder-wine
Note, that if you've previously set a custom icon on the file, within Nautilus directly, you'll have to unset that icon. You can do this by opening the properties dialog for that file in Nautilus, clicking on the button with the icon on it, and choosing "Revert" in the file chooser dialog which opens up.
I have found a very simple solution to this problem.
After a single change, the above folder now looks like this when set to 200% icon zoom level:
It was as simple as changing the "thumbnail-size" value in "dconf-editor" for nautilus to a larger value.
To apply the change, make sure "dconf-editor" is installed in your system by typing the following into a terminal:
sudo apt-get install dconf-editor
After installing, type Alt - F2 to pull up the command dialogue, and type "dconf-editor" to search for it and click on it.
Once you have "dconf-editor" open, navigate to the following location in the left pane:
org > gnome > nautilus > icon-view
See this example image for the location:
The value that needs changed is the "thumbnail-size" value. I changed it from a default of 64 to 128. Depending on your display resolution, you may need to change it to a different value to make things look exactly the way you want. Smaller displays might need a value larger than 64, but 128 might be to large, so try something like 96.
Once that value is changed, exit "dconf-editor". Now the thumbnail cache needs to be cleared to allow that changes to take effect.
First close all Nautilus windows, then type the following code in a terminal (each line is a separate command).
nautilus -q
sudo rm -r ~/.cache/thumbnails/
The first command makes sure Nautilus is closed, and the second clears your thumbnail cache.
Note that this does not affect file or folder icons. Those will still appear to be smaller than the picture and video icons generated by Nautilus (or more correctly generated by ffmpegthumbnailer). This is still a huge improvement for thumbnails in Nautilus even with this shortcoming.
This fix worked on Ubuntu 14.04.1.
Best Answer
My Nautilus does this by default ... I don't see anything in the settings that would enable or disable this functionality.