The biggest problem is that you need somewhere to put the projector where the band won't
cast silhouettes on it. If it's a deep stage then that's fine - put the projector behind
the drumkit - but if it's only a small stage then it could be tricky. Unless the screen
is higher than the band, of course, but then it's not exactly a backdrop.
You're also going to need to get the HD pics over a fair old distance, and this is
likely to be more than a basic HDMI cable can manage. So you're going to want an HDMI
extender of some kind.