Certainly Jim. As an actor or storyteller I use an accent to create a character (I'm not too bad at several accents)and sometimes the script calls for it.

Sometimes when I'm singing a particular song the character of the narrator, or perhaps the nature of the song, sometimes gets me thinking of, for example, Scotland or Tyneside and I might slip into accent without thinking about it (my mother's a Geordie and Dad was Scottish). I used to have a habit of picking up accents if I was around someone with a strong one, so sometimes some stimuli (even something like talking about a place) can make the accent slip without me meaning to (very funny for those around if I'm on the phone, or something).

I don't do full-on imitations of accents when singing unless it is some kind of comic or music-hall song.