HOW-TO: Add Custom Folder Icons for any Theme
I found a how-to for adding custom folder icon to your OS without creating an entire theme.. all you need is the right file manager for your blackberry and few of your favorite icons:.
1) FInd and download / copy folder icons to your blackberry's media card. These icons should be .png files of approximately 64x64 pixels, but any png will work (they are not resized in the OS's folder icon selection dialog, but will be resized on the actual folder button).
2) Install a BlackBerry file manager that allows viewing of hidden OS files, and has a copy / paste operation. For this how-to I will be using BBFileScout.
3) Open BBFileScout and browse to the folder on your media card that contains the folder icon that you would like to add to your BlackBerry OS. If you are going to be adding alot of icons I would suggest using BBFileScouts menu to "Add Dir as Favorite".
4) Select the .png icon file, and then select "Store <image-name>.png on Stack"; now browse back to the filesystem root and then to /system/samples/folder icons. select "Copy file-name.png to.." from the menu to paste the file into this directory. I also renamed them to keep the existing naming structure, but I don't think this is required. The icon is now available in the OS's dialog for selecting folder icons.. If you would like to add more I suggest you also "Add Dir as Favorite", and then use "Goto Favorite.." to jump between these directories
Just in case you are not familiar with setting folder icons, here is how it is done on my BlackBerry Storm 9530:
1) From the home screen "Add Folder", or select an existing folder and choose "Edit Folder" from the BB Menu.
2) Click on the Folder Icon and scroll through to find and select one your newly added icons. When ready, click "Save" ..on my phone the Save and Cancel buttons only work from this dialog when in portrait mode.. if they don't work, give it a try.
Credit: Tutorial: How to customize ALL folders icons in a theme - Discussed in Software & Theme dev forum - PinStack.com
PS.. I got my icons from kde-look.org (a site dedicated to customizing the linux KDE desktop)