How do I edit multiple layers at the same time?

How do I edit multiple layers all at once, the images is phpBB forum images and they look the same at the edges but have different graphics in the middle, I want to edit the edges of the small Icons all at once.

Tanks

Examples of the images:

You use flatten. But once you flatten you cant go back. I skinned a phpBB forum, but got about 90% done and havent gone back to it. The design part was easy, but the layout got annoying. The site is so broken up into includes and sub pages. hehe.