Using images found online
When designing your shirt, the possibilities are endless. The internet offers an ocean of images on which to draw for inspiration.
If you choose to create a shirt design from artwork found on the internet, make sure that you have the rights to do so. A lot of what's out there was made by hard-working graphic designers who rely on royalties and licensing fees to keep creating awesome images.
When you upload artwork to the T-shirt design wizard, you are required to check a box stating that you have the rights to reproduce and sell the design. Selling somebody's design without their permission can have serious legal consequences.
Other copyright and trademark issues
It also might be tempting to create a T-shirt design that includes elements of a copyrighted work or a trademark. After all, social media is full of people posting all sorts of stuff without proper permission. However, remember that unlike a Facebook post, a Bonfire T-shirt will often result in actual profits. Making real money off protected intellectual property can result in severe legal repercussions. Be sure to use caution.