you can change the Windows Login Background in windows seven just few step needed..
Go to Registry editor
for dis type 'Regedit' in run dialog
then go to
search 4 'OEMbackground' if n0t creat by edit>new>Dword-value' n change its value to 1 n okay..
image should hv fulfill folowing points
=> its resolution should b as excect or nearly as ur screen resolution.
=>its max size should be 250KB
=>it should b of your choice:-P
Placement Of Image
copy this image to
if n0t create n paste
Now Restart to get New login screen..