I've not used any wallpaper themes from Cydia, but here's my attempt at helping: Go to your Settings app > Brightness & Wallpaper > Wallpaper and see if those pictures are anywhere in there to select.
If I understand these wallpaper themes correctly, they just put the images into the stock location where Apple puts the default pictures. So, they should be right there.
If not, holler back and maybe someone else (who uses them) may be able to help. Sorry I couldn't help more...
Marilyn