Hi Smilam - I've looked @ Marilyn's excellent post (w/ pics) about 'copying & pasting' which seems to apply mainly to text - however, your question relates to photos - correct?
For myself, this has been a much more irritating process on the iPad - you may want to tell us 'where & how' you are trying to copy and paste your photos, e.g. from a web browser? If you 'tap & hold' an image (e.g. in Safari), a number of menu options are offered, including 'Copy' & 'Save' - copy puts the pic on the clipboard and can be pasted into e.g. an email, while save puts the image in your photo app.
NOW, one of my main problems is copying an image's URL into a forum response; Safari seems deficient in this option - I've had better results w/ Atomic Web - SO, please let us know 'what' you are trying to do w/ your photos and we might be able to provide more definitive advice - Dave