You should consider including a source for your images. Including a source not only gives credit to who made the images but shows you put time and effort into making your post. This may make people more likely to vote on it.
If images are Public Domain or CC0 you could just indicate that at the end of your post. All photos are Public Domain for example.
Finding the original source isn't necessary. A link to where you found it will do.
Thank you for the helpful advice. I usually just focus on the content of the post, and just add photos that are in Public Domain - found with google. It takes me some time and effort to put my post together, for i have to make sure it is understandable and clear.
Updated my post, and will include in future posts every link that was used for photos.
Thank you again.