I have a couple of "hacks" to make sure pictures and information you use on your website are true.
The first place I go to is Google Images. They have an easy way to locate specific pictures. If I wanted to look to see if someone was using one of my pictures, I can easily drag the picture from my blog to Google Images.
Same instructions go with searching for a image that is not yours. If you find a nice picture on Pinterest, and you don't know the original website, just drag the the picture again in the image search box, and eventually you should be able to find what you are looking for. I use this especially when I'm looking for crochet pins from Pinterest that do not have the original link to the tutorial.
I found this picture on Pinterest, with a link to media.Tumblr.com. I tried looking for the original blog, but sadly I couldn't find it.
Pictures get taken and claimed on blogs as their own, so if you'd like to keep an eye on your pictures make sure you have a watermark, or mark your pictures with your blog name. You can use http://picmarkr.com/ or microsoft paint/photoshop to give your photos a mark. Sometimes the only way I can find a blog post with the picture is looking up the website.
Sometimes it's tough finding the right photos for a blog, and I want to make sure to give credit to the right person's work!