I do not have experience making lj layouts, but there are a lot of people who design layouts for people to use. Also many websites that offer them for free
here are a few examples:
LJLAYOUTS.org____livejournal layouts [s1,s2,free,paid], tutorials, icons, etc!
paintedlayouts : free livejournal layouts.
Free layouts
FREE LJ layouts- Links Directory
Also, if you have your own header here is one way to add that to any layout that is designed correctly:
Adding a Header Image
Also, don't forget, there is a thread on Webmasters board on lj help
here if its not working
Does that help any?