OB is just another allele of YB. OB x YB makes an Ivory. Some people argue that all OB x OB will produce a GraphiteIvory but I have yet to see any documented proof of this.
I have heard it argued that the white of a Pied is brighter/cleaner than the white of any BluEL, so it might not be a totally pointless project in that regard.
Other white snakes:
WomaPied and ChampPied can be all white
There are some lines of BlkPastel that will occasionally throw all-whites when combined with Pied in the same manner as Spieds
Any of the superforms in the BluEL group (with the possible exception of the Daddy allele) when combined with Pied; e.g., CrystalPied, PotionPied... But, as noted above, you get microphthalmia.
Snows (already mentioned) and LavSnows
If you stack enough other genes in Champs they seem to wash down to near-white, e.g., SuperPastel Champ Fire Lesser
Albino SuperBlk/SuperCinny/8Ball though these might blush yellow with age
Albino Suma might as well though I suspect they might blush yellow the same as above