You should do your best to gain permission for the use of photographs or images in your thesis or dissertation. For information and request letters on gaining permission, see the ETD Copyright website. 

If you cannot gain permission, you can consider using another photograph that will serve the same purpose by another (hopefully more responsive) owner, if possible. However, if you wish to use these particular photographs, you have a solid Fair Use argument here since this is a scholarly work.

For information and tools for thinking through Fair Use, see our Guide on the topic. 

There are guidelines from the Visual Resources Association about the Fair Use of images for teaching, research, and study. Their policy document is linked below, and on page 12, you can see some best practices for using images in a thesis or dissertation if you cannot obtain permission. These include having the images be the subject of commentary, using lower-resolution images if possible, and giving good attribution.

http://vraweb.org/wp-content/uploads/2011/01/VRA_FairUse_Statement_Pages_Links.pdf

The University of Southern California Library has some more excellent information and suggestions (especially on documenting and citing images), which you can find here: http://libguides.usc.edu/c.php?g=235130&p=1560458

To conclude, if you use images for which you cannot obtain permission, follow the guidelines above and document your attempts to gain permission (this is called doing “due diligence”).