There is a lot of leaked images floating around everywhere now. For the most part they are on forums at the moment, so I have linked the pages, so you wont have to wade through page after page. The formations for the Tyranids Leviathan are looking really good, and I think that Tyranid players will be rejoicing with these newly released formations.
Here is the leaked release list for this week. Images found here
They are on Dakka, and there is a lot of leaked images there, including the index page, all the Warlord traits
Here are the 12 datasheets for Tyranids
Mucolid Spore Cluster, Zoanthrope Brood, Maleceptor, Toxicrene, Tyrannocyte
Hyptertoxic Node- Poisoned models gain the instant death rule on a roll of a 6, and Toxicrenes gain instant death on a 5 or 6. also the Hive Tyrant has Toxic Miasma and all tyrants within 12" can use Toxic Miasma each turn.
1 Hive tyrant
Neural Node- Shadow of the warp is 18" on the maleceptor, and units can re-roll 1's on psychic tests
Skytyrant Swarm- Hive Tyrant gaints 6" synapse, and the gargoyles can look out sir on a 2+. The tyrant and gargoyles are a single unit.
1 Hive Tyrant
2 Gargoyle Broods
Skyblight Swarm- Gargoyle broods gain objective secured, and destroyed Gargoyle units come back on a 4+
1 Hive Tyrant
1 Hive Crone
3 Gargoyle Broods
Sporefield- formation has infiltrate, and anytimes unit is destroyed, on a 4+ it comes back in ongoing reserves.
3 Mucolid Spore Clusters
3 Spore Mine Clusters
Skytide- synapse bonus of 6" for the hive tryant from the skyrant swarm, and can re-roll to bring back destroyed units.
1 SkyTyrand Swarm
3 Skybright Swarms