When preparing lectures on problem solving related topics for undergraduate, I sometimes wonder if it is a bad practice to use examples from the textbooks. Will students think the instructor is lazy and merely follows steps written in the textbook? If it does create negative impression, does it make it a little better if we go through one or two problems after explaining an example from the textbook?
Personally, I think that the source of an example doesn't matter half so much as the quality of the example. If you've got a really good example that came from a textbook, then that's just as OK as having a really good example that came from another professor or one that you made up yourself.
The question, to me, is whether you've made the example your own. If you've taken the time and effort to really understand the example, then when you present it, you will not present it exactly the same way that it was presented in the textbook. Your own understanding of the material and personal style will color the presentation, marking it with commentary, pacing, and choices of emphasis, all of this together giving your own "voice" to the presentation. I think that students recognize when somebody is presenting material in this way, even if they don't know how to name it as that. They may or may not like your style, but they certainly will not think you are merely following steps from the textbook.
Likewise, I think that there is no reason to hide where you've gotten an example, particularly if you give your reasons, e.g., "this example we're going to work is one from the textbook that gives a very nice illustration of the consequences of Kirchhoff's Law." In fact, giving credit to your sources is a good way to inculcate more of the culture of academic honest in students by example, as well as an aid to students who might want to go over the example again with the textbook.