I have never tried to use my treadle without power for lights to see by, but I do collect oil lamps, and have one of those LED emergency lights plugged into outlets. One thing we've always done at my house when the power goes out is to set all of our candles or lamps on a mirror, to reflect the light as much as we can. Mom even has a couple of older home interior wall sconces with a candle holder in front a mirror. You'd be surprised at how much of a difference that can make!
I once found a boot box full of candles at a yard sale for $4, years and years ago. They're mostly tapers, and I still haven't made a dent in that box!