I would guess that most (more than half, but possibly 90%+) products that display art and designs of which are sold on the internet (as well as comic conventions) are counterfeit, illegally unlicensed, infringing copyright or stolen from artists without permission.
The state of affairs regarding stolen artwork on the internet is ridiculous. An epidemic one person on their own, or even thousands together could never hope to even reduce by a tiny amount. To say this upsets me and to attempt to make people aware of what's going on here seems like a wasted effort while the sounds of a thousand virtual cash registers ring from the profits of stolen art every second of the day!
I don't even look for it, but I see it all around me. I often recognize my favourite artist's work being used on questionable products by relatively unknown online marketplace retailers and know a lot of the fan art and concept art I see isn't being licensed to certain low-grade knock-off merchandisers. Instead it's simply been saved off of the internet and slapped on top of a product...
And then it happened to me. I did a reverse image search on one of my works to find it for sale by three different Chinese retailers on Aliexpress and two other separate T-shirt and apparel stores! I'm attempting to get these works taken off, but it's not always easy. Stores often ignore or don't seem to take these kind of complaints seriously~ so long as they're making money and aren't getting an official 'cease and desist' letter through the post, they'll carry on profiting from a stolen work, while the original artist gets a zero percent share of the income it generates.
To help combat this in the future I've spent a few hours lowering the resolution of each image in my portfolio on this site. They should still look fine, but originally I was hoping to future-proof by posting larger sized images as screen resolutions continue to get bigger and that's something I won't do anymore. I've also applied watermarks to the bottom corners of selected works. The only trouble is, I can't stop people stealing 'without watermark' images I've already supplied added to my online 'print on demand' stores such as Society6 and DesignbyHumans 🙁
I appreciate that most buyers wont even consider there could be an issue with the items a shop has to sell, but I just ask that before you buy a print, t-shirt, mug, key-chain, etc, please do you best to find out if it's legit and make sure you're not lining the pockets of a thief. Buy from original creators or verify the products being sold are official and licensed. In the world of anime, comic and gaming merch it doesn't take too much practice to spot a fake from higher quality original.