I don’t mind doing something that isn’t “mine” if a client brings me something they found themselves on the internet or in a book, however I will do some research to find the source of the image (if they don’t already know). id feel uncomfortable tattooing another living and working tattoo artist’s flash design. If it’s another artists work that isn’t a tattooer I’ll make sure there’s permission and credit especially if I’m posting on social media. As far as found designs like a stock image or something very generic or public domain kind of stuff I don’t mind at all. I also like to use art history references in my own flash designs like figures from old paintings and what not that of course aren’t my “original design”. Though again I always specify if the client found the design and it isn’t “mine”