Some simple comments (from someone who has had a lot of hit work ripped off).
.gif and .jpg diagrams are much less likely to be pinched than .pdf eg
http://home.no.net/origami/
Hand drawn diagrams are less likely to be pinched than computer drawn ones
http://www.fishgoth.com
Put your name in big letters at the top. And at the bottom and sides. So that people know who the creator of the diagrams are.
Be prepared to still get ripped off, have diagrams stolen, and other internet bother.
Be prepared to send VERY threatening emails, addressed to 'Internet service provider', asking for the entire offending website to be taken down and personal details provided for your lawyer. cc the email to the website owner. A grovelling apology usually follows in minutes. It doesn't matter if you don't know the ISP's email; send it anyway. All that matters is the offending website THINKS that someone has sent the relevant email to the ISP
However, this will get your name known, and if they are good enough, will get you fan-mail...
I once set up an origami PLC. But the business folded.