I've always wanted to implement video backgrounds, but the technical complexity and issues to work around have always put me off from implementing it thus far. However, after a couple more people have asked about it, I've decided the next major release is probably the time, providing we don't run into any unforseen difficulties.
I've started to do some work and a few hurdles have been solved, but there's still quite a lot to do. But all going well, the next version of Quelea should support nice looking video backgrounds. Swish!