Can I use your designs on another product, like a t-shirt?

No. Sorry we offer no rights or allow NO premission for anyone to use any of our designs on any  other products,  Our products are exclusive to stickerheads.com.  The designs are our intellectual property rights and protected by law as such.

What is Intellectual Property Law? 

Intellectual property law deals with the rules for securing and enforcing legal rights to inventions, designs, and artistic works. Just as the law protects ownership of personal property and real estate, so too does it protect the exclusive control of intangible assets. The purpose of these laws is to give an incentive for people to develop creative works that benefit society, by ensuring they can profit from their works without fear of misappropriation by others. 

You can read more about intellectual property rights by clicking here:
https://www.hg.org/intell.html