Give Credit where it is Due
This applies to almost all things and it works on Pinterest as well. Since you probably won’t be posting original content every single time, make sure to give credit to the original source. This is highly ethical and it complies with the Pinterest guidelines as well.
At the same time, don’t directly pin an image just because you saw it on Google and you liked it. Chances are, you will be able to find the original source by clicking on the image or the link. Make sure to provide information on the name or website where you got your source. You also wouldn’t want to see your photograph or your works online without being credited, do you?