If you mean guides, there are on developer.apple.com
If it's about resources, then you need to actually go to google and type in free stuff Like glyphish free icons etc ^_-
Oh... and to make your own images... find a good vector drawing program and learn to use it. I LOVE iDraw on my iPad (they also have a Mac version). Inkscape is free and not to bad for the Mac.
There are tons of vector tutorials on youtube. I have found it very easy to create great looking images to use in apps. The only thing that will hold you back is artistic vision!
I'm not quite sure if this is what you're really looking for, but here's a tutorial covering how to customize the appearance of various standard UI elements: