So I was covering a corporate event the other day and one of the speakers asked for a cool portrait at the venue. We had 2 minutes before his taxi arrived and I had no way of lighting him nicely as I had one flash for corporate "run and gun" and couldnt bounce it as the ceiling was way above us. What to do? I positioned him in the frame so his suit was silhouetted by the light coloured marble and his hair and face were backed by the dark statue.
It's high iso grainy photography but by being intelligent about the composition allowed me to get a interesting contrasty shot in a terribly low light lobby.
Try this yourself with your phone in a bar next time you want a picture. Put your subject against something that contrasts with their outline, then if it does get grainy because of low light you will still get something useable because you brain perceives contrast between two areas as sharpness. As always this is a free tip, just spend some time practising with what ever camera or phone you have with you when you are out.