No no no, sorry, I'm not good at explaining complicated things in english
Each theme has these backgrounds (separate images): - desktop wallpapers (there's four of these) - wallpaper for clock - wallpaper for lockscreen - wallpaper for application manager With Pleego I have used the same "Meego people" background for all of those, but they still are all separate images and chaning one won't change the others. If you change the homescreen wallpaper, it won't change images for the rest of the things mentioned earler.
If you wan't to change those backgrounds, you need to manually overwrite these images with your own: /opt/plastic-schemes/SCHEMENAME/backgrounds/clock.png /opt/plastic-schemes/SCHEMENAME/backgrounds/lockslider.png /opt/plastic-schemes/SCHEMENAME/backgrounds/applicationmanager.png And then run the setup again.
About that lockscreen -issue. You have rebooted after changing scheme have you?