Users of Garmin's Nuvi, Zumo and Streetpilot c500 series can enjoy a wide selection of free vehicle icons for their devices. These free vehicle icons are available at Garmin's website. More icons are added from time to time!

Instructions on how to install these vehicle icons are available here .

1. At the main menu, press "Tools"
2. Press "Settings"
3. Press "Map"
4. Press "Map Info"
5. At the Map Info page, you can view the list of maps currently loaded into your Nuvi. You can also activate (check) or deactivate (uncheck) them

Source: malfreemaps.com

When you connect your Nuvi to your PC or laptop with a USB cable, you will notice Nuvi's content to be something like below:

Below is a brief explanation of the folders and files:

• Diag folder - used by Garmin
• ExtData folder - used by Garmin
• GPX folder - stores your trip log. You can open the GPX files within this folder with Mapsource
• Help folder - stores help files in different languages
• JCV folder - stores Junction View files on models which support such feature
• JPEG folder - stores Nuvi's default pictures and splash screens. You can add more jpg files into this folder
• POI folder - stores custom POI and travel guide files. These files are with .GPI extensions. It is ok to delete these files if you are sure you don't want them
• RemoteSW folder- used by Garmin for unit software update
• Scrn folder - stores your screen capture images. The files are in bitmap (BMP) format and could be opened with Window's Paint application
• Text folder - stores default and custom messages and keyboard layouts. These are text files with .GTT extensions. You can edit them with a text editor.
• Vehicle folder - stores Garmin vehicle icons. Files are with .SRF extension. You can add and delete these files. 
• Voice folder - stores Garmin voice guidance files. Files are with .VPM extension. You can delete unused voice files but do so with care.
  
  

• GarminDevice.xml - stores information about your Nuvi to facilitate tranfer of data to/from your Nuvi. Leave this file alone.
• gmapbmap.img - Garmin base map (worldwide map)
• gmapprom.img - Garmin pre-programmed (preloaded) map. Back up this file before deleting or overwriting it.
• gmapprom1.img - Garmin pre-programmed (preloaded) map. Back up this file before deleting or overwriting it.
• gmapsupp.img - This is the common file name for Garmin maps.
• gmapsupp.unl - Unlock code file for Garmin supplementary map.
• gmaptz.img - Garmin time zone map. Leave this file alone.
• GUPDATE.GCD - Used for Garmin firmware update. Leave this file alone.
• Locales.xml - stores default language, currency sign, time zone, etc settings for different countries. Leave this file alone
  

Anywhere within your Nuvi menu options, holding the back button for a while will bring you back to the main menu.

Source: malfreemaps.com