I love poop stories! LOL
I use pixabay.com for a lot of my stock photos and http://giphy.com for animated gifs. Check out http://steemimg.com too.
If you are using all pics from a creative commons source, you can cite it at the bottom of your post. That's the quick and dirty way. I personally choose to try and link each photo or clipart that isn't mine to the original source. It's time consuming, especially if you use a lot of photos.
[stock image] (The URL to the original source goes between the parentheses )

Take out the extra space between the brackets and parentheses and you are good to go. It's exactly like the code to add pictures minus the exclamation point. :)