Great question, Deepak! They are both grammatically correct, but have different meanings, as there are different kinds of possession. A photo of you is a photo in which you appear — you are in the photo. A photo of yours is a photo that you own — the subject could be anybody, or anything. Alternatively, “your photo” would be ambiguous as to whether you are in the photo or whether you own the photo (and would usually be considered definite, rather than indefinite). In the example you gave, it is probably “this one of you”.