"¿Quieres mi foto?"
Traducción:Do you want my picture?
I have researched, and "Pic" is ok, it's a short form for PICture (sorry capital letters are mine, for emphasis ), English is a very flexible language, English people like to use a lot of short forms but in some cases this must be used carefully because some forms are incorrect and even considered lazy or lack of culture (for example ..."Ain't"). Obviously, see the context, familiar or formal. Anyway I think Duolingo not accept this short form as an answer. Good luck!
I don't know if I have ever heard "pic". It would be a slang phrase, and I don't think that common.
I would say they should not accept it. In part, because we are focusing on written language in DL. What people say is not typically how the language is written.
For example, I never see my students writing " I wanna", even though I have seen that asked here in DL if it is OK here on DL. My students make many other mistakes, but they don't write "I wanna/gonna" or "didja see...", etc.
Nor does DL seem to accept texting abbreviations. My feeling is that we would be learning to write well. If we know how to write well, we can always write badly on our own time, or when we want.
Further, I have no desire to practice writing bad Spanish -- I am quite capable of writing Spanish poorly without having to learn how to write it poorly /badly.
And I have have seen numerous examples of bad English here on DL, by people who I believe are trying to write well.