Are there any open source sprite format?

PNG just plainly sucks. I has no support for animations, timing or delta compression and sequence names. Also, PNG is slow at random access (you have to decompress image before use). Proprietary formats (like Diablo 2 DCC) are much better, but highly specialized for their games: some have no true color, other have no directions.

>>80
"Performs" WRT compression algorithms usually means compression ratio. DEFLATE compresses better but is slower than LZW. There's nothing wrong with that.

DEFLATE performs sufficiently in fast in practice for most applications. Many web pages are transparently compressed using it, for example (including all HTML served by this domain).

In fact, seeing recent developments, it'd be appear there's a demand for better yet slower algorithms, a demand the Russians are filling.