Hello there,
Most of the time, I use Quelea for my life group for everything including songs. I know a similar feature has already been requested in the past. I would like to have the feature of adding a worship pad / backing tracks to the songs. This would allow me to have the audio during our worship to have a more fuller audio experience than just me. I know it has been suggested that play songs separately, but most of the time, I’m the only one controlling things. So having the worship pad play when a song is displayed would be a big help. 
In addition to this, it would be great that each pad would fade in, and at the moment of transitioning out of the song, the audio pad would fade out rather than abruptly stop… and if another song is on the queue, the next worship pad key fades in. I hope that makes sense.
Would appreciate if you can add this to your list of features.