We try and use our own photos from our own travels. Sometimes we can't (if we didn't have a good photo, or didn't take one!).
In those cases we either resort to Facebook (if it is a bar/company/club/business) and generally use the cover image. We feel this is in fair use, but if you have any issues at all we will remove it ASAP.
Other times we might look for public domain images, or creative common licensed images (such as from Flickr). We always credit (in the footer) but if you own the rights to an image and want it removed please just let us know, and we will remove it ASAP.