first you must power on the hidden files in windows in the control panel in folder options
and power on the permission to view system files and hidden files

after go in the folder that you want tu customize and create a new txt document, after put in it this content and replace the string C:\images\myimage.bmp with your image place:

[ExtShellFolderViews] 
{BE098140-A513-11D0-A3A4-00C04FD706EC}={BE098140-A513-11D0-A3A4-00C04FD706EC} 
[{BE098140-A513-11D0-A3A4-00C04FD706EC}] 
Attributes=1 


save it in the folder with this name:

desktop.ini



and the result is like this:







you can insert image in other format,not only bmp ;)



important:

when you save the desktop.ini file, select all files in the notepad,not txt ;)
      
IconArea_Image=C:\images\myimage.bmp