I ended up jailbreaking my iPhone 3GS(new bootrom) 4.2.1 with the latest version of redsn0w. Everything is working fine, except I've downloaded a few lockscreen themes. The slider and colours work fine, but for whatever reason the theme's wallpaper isn't transferred. Does anybody have a fix for this?
Did you go to Wallpapers in your Settings.app to set the wallpaper? There are two types of themes on iOS 4. Some themers set it up to work with the native wallpaper function, which upon installation of the theme will put the image in the wallpapers tab. Some themers do differently and put the wallpaper that will override the native wallpaper option by putting the .png or .jpg file within the theme's base folder. It looks to me like you in particular have to set your lockscreen wallpaper in the native wallpaper feature through Settings because if the wallpaper was included within the theme, it would've showed up by activation of the theme in WB.