Is it possible and, if yes, how?
I only found "flagging for deletion" and I don't think that really applies.

Not possible. Why? Artist doesn't approve? Sadly, if that's the case then the artist will need to request a takedown. Please refer them to http://www.e621.net/static/takedown as politely as possible.

Alternatively, you could PM a mod and ask them to take it down. There's no guarantees, but if you offer a polite explanation then they might be able to help you out.

Shatari said:
Alternatively, you could PM a mod and ask them to take it down. There's no guarantees, but if you offer a polite explanation then they might be able to help you out.

Sure, maybe :V
If you haven't insulted us or been all yelly and capslock when wanting something not retarded, we should help you out.