Not citing the source of photos is plagiarism. Here is a post on why this is bad, and here is how easy it is to find allowed photos.
Creative Commons: If you are reposting under a Creative Commons license, please attribute and link according to the specific license. If you are reposting under CC0 please consider noting that at the end of your post.
If you are actually the original author, please do reply to let us know!
Thank You! ☙
Every photos I have taken from an open source. I'm not pretender for a unique content, and I don't care about any license. Thank You!