What is the biggest texture that the wc3 engine supports?

The question refers to the texture resolution. The biggest textures I have seen were 512x512, the default loading screens are split into multiple smaller textures so that the biggest parts are no bigger than that. Is that the maximum? I was thinking of maybe using 1024x1024 textures for a skybox (single player, so filesize is not (that much of) an issue), because a realisticaly sized sun in the sky would only be 2-3 pixels in diameter on a 512x512 texture which would make for a crappy close-up of a sunset.

Perhaps I should just exaggerate the size of the sun instead? I'd rather do that than chop a large texture into smaller ones and make a mess in the import manager, but if 1024 textures are supported that would be ideal.

trial and error. just test it.

Can you use a custom sky model?

1024 is impossible sadly. I usually create my textures at that resolution, and when i try to export from max while the texture is still high rez it gives an error. I think the max size may actually be 778, but i'm probubly wrong.