I copied the following from the man page:

type (TYPE [, ARGS]) 
     This method will send the TYPE command to the remote FTP server t
+o change the type of data transfer. The return value is the
     previous value. 

ascii ([ARGS]) binary([ARGS]) ebcdic([ARGS]) byte([ARGS]) 
     Synonyms for type with the first arguments set correctly 

     NOTE ebcdic and byte are not fully supported.
[download]

Set the type to binary for images. Usually the default is ascii and your image file will end up as garbage once it is downloaded to your end unless the type is changed.

I hope this helps.

Mick