Can a .BMP file be stored in an HTA (HTML/VBScript)?

I've noticed in a backup of my FireFox bookmarks that the icon which is displayed to the left of each entry is held as a character stream in the A tags. For example:

ICON="data:image/png;base64,iVBOR [data removed to shorten example] rkJggg=="

I have 3 BMP files (2 are 4x20 (249 bytes) and 1 is 102x82 (24.7 KB)) that I would like to hide within my HTML Application so they don't get lost.

The larger one appears 3 times in the style tag as follows (1 occurrence shown):

<style type="text/css">
#frmMainBody
  {background:grey; background-image:url('Background.bmp'); margin:0;
   padding:0; font:normal 10pt Microsoft Sans Serif;}
</style>

The other two appear in a VBScript subroutines as follows:

Sub Button_Glow
  ' Highlights a button when the cursor hovers over it.

  With Window.Event.srcElement.Style
    If .BackgroundColor <> "Lavender" Then
      .BackgroundColor = "Lavender"
      .BackgroundImage = "url(Glow.bmp)"
      .BackgroundPositionY = -2
      .BackgroundRepeat = "Repeat-X"
    End If
  End With

End Sub 'Button_Glow

Is this possible ?