Am I allowed to just Google what picture I want and use it in an article, or is that considered copyright infringement?
It really depends on the image that is used. The general guidelines for using images can be found on the page How To Write An SCP under the "formatting" tab. More complete rules for content usage can be found in the Wikidot Terms of Service. I hope this helps.
To be more accurate, we cannot somehow magically give you permission to use an image. You should have a license for any images you use, whether that means that you took the photo yourself or otherwise asked the copyright owner for permission to use it.
If staff receives a cease and desist or DMCA takedown notice by the proper copyright holder of any images you use, we will remove it without warning (and you will probably be banned for illegal activity).