Ok everybody, I have figured out the fix to change the background of your multitasking/folder/folder icon backgrounds (tested on iPhone 4). If you recall there was a similar issue with 4.1, but unfortunately 4.2.1 doesn't have the same fix. Here are the steps:
First, go into cydia and install whatever Multitasking BG theme that you desire. Once installed go into iFile or an SSH program of your choice (ifunbox, iPhone Browser, etc...) and go to the directory var/stash/Themes.yicaPY. Find your desired theme and enter that directory (EX: Black Multitasking). Then enter the directory bundles/com.apple.springboard. Here you will see all the files of your selected Multitasking BG theme. You must add "~iphone" to every file right before the extension name (.png).
*YOU MUST ADD "~iphone" (without " ") TO ALL FILES IN THIS FOLDER!
Once you have completed this exit your SSH/iFile and go to Winterboard on your iPhone and select the multitasking theme you just edited. Respring your device. If all your changes (mainly in the multitasking bar or folder drop down) have not changed then you can do one of two actions. 1.) you can go back into iFile/SSH program and go to the directory var/mobile/library/cache and find these four files:
com.apple.SpringBoard.folderSwitcherLinen0-3. (each of the four files will be numbered differently, 0-3). DELETE ALL 4 OF THESE FILES.
or 2.) you can go into cydia and install fswipecache, which will do the same thing except you'll only have to press the icon which will be located on your SpringBoard.
REPRING your iDevice again and then all BG's should be changed. Remember, there are some BG themes that will not work for one reason or the other. It could simply be the PNG's are not the right size or that are missing files that will not allow it to work on iPhone4. If you have any questions feel free to post a reply or PM me. I'll try to make a YouTube video for this fix. I know a lot of people have been wanting this fix. I hope I've helped.
My pleasure!!! I've noticed that once you rename those files and you go to uninstall that theme it will not delete them out of WINTERBOARD, so you'll have to go into that Themes directory in stash again and just delete the actual package from there and then it'll be gone from Winterboard. That's the only place that the file remains. The package won't actually work after uninstalling it from cydia so like I said, IF you have that issue just go to stash/Themes.yIca like I mention in the above post and manually delete them there to be gone from Winterboard.
hey bro, i tried this with the "Blackwood Multitasking" and it didnt change anything....you have any clue what i could do or is it just not going to work thanks
Let me install it and see. Are their any X2.png files (like folderBGX2.png). If not they r not compatible with the retina and will not work. I'm pretty sure all themes and multitasking BG's need those X2.png files on iphone4, cuz they are a higher resolution.