If you mean crossbreeding...then mix veiled with what? The different varieties of panther chameleons are still all the same species, just different colors so it's not really crossbreeding per se. They are all the same. Veileds can breed with other veileds but that's it.
The thing is, there aren't really various breeds of veiled chameleons like there are with panthers. Panther chameleons as a species are spread out over a number of small islands, which is why they're varied like they are. Veiled chameleons live in Yemen, so there is not nearly as much variation. There are a few mutations of veiled chameleons that owners have bred, like the transbald veiled chameleon: http://i300.photobucket.com/albums/nn12/justinigor/Misc Chams/Transbald20Veiled20016-LOW20RES.jpg