Design question

I’m just starting to learn a little about this process. I’m not a very experienced illustrator, but I’m interested in adapting some existing graphics and patterns to carve and make prints. Is this ethically problematic if I take some existing clip art or similar and modify it to make my own linocut and prints? For example taking a bread clip art and making a print for cotton bread bags. Do most people design their own patterns here? Do you use a computer to create them, or just sketch them?