Currently there is no method for customising this. However you can easily add ~100 - 200 songs with a single click using the add youtube playlist option.
For example "PLFgquLnL59alCl_2TQvOiD5Vgm1hCaGSI" for the most popular 100 songs.
If a viewer requests, it will be prioratised automatically to be played in the next non-streamer requested slot. So you do not have to worry about filling it up and blocking viewer requests.