I wish i would have seen this topic this morning. o.O I just did an invoice change on my site today. It's modeled after Amazon's packing slip that they send out with all their orders. We're planning to print one of these out landscape (without IE headers or footers) and include it as a packing slip with our orders. On the top right hand corner is a mailing label.
http://www.aheadgames.com/images/invoice.gif
My invoice took editing of a couple template files, no php changes. I'll leave releasing an invoice mod to anoack though. I don't want to step on any toes.
