Right now random in Pixelblaze is a true random number generator, or more accurately a PRNG periodically seeded by true random bits.
I think a seedable PRNG would be a nice API to add, especially if speed was essential. Perhaps along with noise functions.
(Edit 9 months later: A seedable PRNG has now been introduced as prng(seed) in firmware 3.30. Here’s the release announcement)