Which "folders" are you talking about? The main category icons like Game, Network, Video, etc.? Or the icons of items under the category?
Currently there is no way that I know of to edit the main category icons, as they are stored in encrypted .sprx files that we haven't cracked. The item icons however may be manipulated by editing their .rco file. Check this thread: http://www.ps3news.com/forums/ps3-ha...er-113703.html