I know that I can’t just take someone’s photo from google images and use it on my site without looking into the licensing, but could I take a photo of let’s say a generic wood desk or pen and trace it for use in my illustration without worrying about getting sued?
Is it unethical or bad practice to do so?
This being a legal question, it will vary from country to country. I’ve always been told that tracing an image will result in a so-called derivative work, which owes copyright to the original image’s author.
This being a legal question also requires the disclaimer that I am not a lawyer, that my answer holds no legal value, and that I don’t accept any legal responsibility for it. If you want to be sure, contact a copyright lawyer