What about Shockwave Flash? There is some code in PHP that can create flash movies, thus getting around the .gif issue on my side, and using a format almost every graphical browser can support (compaired to MNG support...)

Are there easy to use Flash libraries for Java? If not, a PNG image sequence might work, I'll just need to figure out a way to convert it to a flash movie either directly in PHP, or via a command line linux utility.