Did you figure it out yet? I managed to swap the lockscreen on the atrixblaze rom to the stock lockscreen (just to see if i could).. and it was pretty simple.
You need an apk tool like APK Manager or the MultiTool (i did it with APK Manager, since i read that there may be some issues with the MultiTool), then copy to your computer, and using APK Manager "extract zip" the framework-res.apk, swap out the lockscreen image file, and re-zip the apk with the APK Manager (it gets more complicated if you're editing xml files, but for images only this works well). Copy the modified framework-res.apk to your sd card, then using root explorer, copy it to your /system folder (you need to copy it here before moving it to the framework folder so you can change the permissions). Change the permissions to chmod 644 (like shown in the 3rd attached pic), then MOVE (do not copy) to the framework folder. It will ask you if you want to overwrite - say yes. Reboot. And done.
But, I didn't see a lockscreen file in SCV5, so this may not work for you at all. You could try to add it and hope that everything that references that image is still intact in the xml files..
: Please install the CWM on Boot before you try swapping your framework-res.apk, it can save you a lot of trouble if something goes wrong