how can delete istock image? i can't find option.

How long is a piece of string?
(Clue: you'll need to tell us from which site/s you wish to delete your image from.)

i know how long a piece of string is

delete a photograph from http://www.istockphoto.com/
photo was accepted got stagnate and needs to go. edit image screen has no delete option

Sorry, I misread istock as stock. 

1. Go to the file page in NEW VIEW - NOT Classic view.
2. Near the top right of the page it says 'Maintenance'.
3. Hover over the word Maintenance, and you have two options, 'Edit File Information' and 'Deactivate'.
4. 'Deactivate' is the one you want.