Zero Kai supports loading various ITP formats. The ITP format from the PC version is very different from the one that Zero Kai actually uses, but the game will gladly load both and more.
However this PC format is undesireable because it's limited to a 256 color pallete.
Files from Celceta seem to be compatible, or at least similar. It looks like the game will also load Ys 8 files (with "ITP" header on the start of the file).
It seems there was an attempt at re-encoding Ys 8 ITP (viewtopic.php?f=12&t=14852
) but it stalled on nothing.
It would be great if that gets picked up again or if someone wants to take a look at these new files instead. Either of them would benefit localization projects for these versions.