Nevermind, changed it manually:
0) login as administrator, Run->"takeown/f %systemdir%\imageres.dll"
1) get latest version of resource replacer from here: h__p://angusj.com/resourcehacker
2) open file %systemdir%\imageres.dll
3) open branch "IMAGE", then "5031" and "1033"
here you will see your default windows logon screen image
4) click on "1033" with right-button and choose "replace resource"
5) "Open file with new resource" and find your 1280x1024 jpeg wallpaper (use Paint for file conversion, if needed)
6) Fill in "Resource Type" field with "IMAGE"
7) Fill in "Resource Name" field with "5031"
8) Fill in "Resource Language" field with "1033"
9) Press replace button and save the file
10) Press ctrl+alt+del to check the logon screen
Caution:
1) You might get error while saving the new file as the old one might be in use firing the access violation error. The best way is to boot-up a live cd/usb and replace the file from there or schedule a replacement batch on reboot.
2) If your replaced image is not shown immediately after you pressed "Replace" button and the tool hangs for a minute or so and you see array of numbers, then your image contains metadata and needs conversion through Paint.