Generally, images on Wikipedia or Wikimedia Commons are open access, but some are more open than others.
There is no one-size fits all rule. You have to check the terms of the license of each photo/image and abide by it.
This photo is, in all likelihood, public domain. The reasoning is listed. This photo can be used freely.
This is a public domain image. The user has released it into the public domain, so you may use it.
This photo is a contribution by the Wikipedia user Daredot, but it is released under a Creative Commons Attribution-Share Alike (BY-SA) license. Generally, Creative Commons-licensed works on Wikipedia use this particular variation of the Creative Commons license.
Under the terms of this Creative Commons license, you can use the work only if you attribute it and license your work under the same terms (Share Alike). This is not going to be the case for your video, so I suggest you avoid the Creative Commons licensed photos on Wikipedia.
Keep track of all the images you use. At minimum, you will want to note the URL of the Wikipedia/Wikimedia page stating the provenance and license of the image. You can also save the page as a PDF and store these for reference.
Another way to find Creative Commons images that you can use - but avoid the non-commercial and share alike-licensed photos - is to search Flickr (instructions here). You will have to note and abide by the terms.