Anyone know law? Can I use these pictures on my website?

I started micro-niche site a while ago and am heavily using pictures gathered off pinterest etc...To build more authority / " sharability " to the website I would like to use tutorials from other authoritative sites in the niche and re-write the entire tutorial in my own words. However I want to use the images from the other sites. This sounds like copyright infringement to me but I know the laws are very gray on this subject.

I started to read some on the fair use doctrine and this quote comes up a couple of times.

quotation of excerpts in a review or criticism for purposes of illustration or comment; quotation of short passages in a scholarly or technical work, for illustration or clarification of the author?s observations;

It's not too specific on what they mean by 'illustration'

Here is the doctrine url: http://www.copyright.gov/fls/fl102.html

If no one here knows the answer then I'll post on a legal forum. Just trying to stay out of legal trouble.

If you're truly concerned with legalities,
1. It's against Pinterest's terms to use images from Pinterest on other sites.
2. That's also a violation of the image owners' copyrights.
3. It's definitely a violation of copyright to take and use an image from another site if you don't own the rights to it.
4. The quote you mention is talking about "quotation of short passages" - the word illustration is not used to describe photos or pictures, it's talking about words that illustrate or clarify a concept. It's talking about quoting text.
5. Chances are slim anyone would ever say anything, but you're asking about the legalities.
6. I'm not a lawyer and this is not to be construed as legal advice.