I am currently in the process of building the following list at just under 2000 points.
HQ - Flying Hive Tyrant with two sets of Scything Talons
Elites - 3 Squads of 3 Zoanthropes
Troops - 2 squads of 10 termagaunts and 2 Tervigons
Heavy Support - 2 Carnifexes each with two sets of twin linked Brain Leach Devourers
Fast Attack - 2 Harpies and a squad of 14 Gargoyles with Adrenal Glands (Poison)
I am still in the building phase so have not played this list.
What I am hoping for is as follows,
1) Early Pressure via the Gargoyles and the Hive Tyrant backed up with Strangler Pie Plates from the Harpies
2) Means of getting rid of the machines via the Zoanthropes
3) Cover for the Carnifexes via the Zoanthropes
4) Largely going to ignore fliers, but I have Zoanthropes and Twin Linked Brain Leech Wormed Carnifexes if I absolutely have to deal with these. I am hoping to get "Ground Cover" Superiority and for my opponent to find that fliers can't hold objectives.
5) I am guaranteed 4 squads of Termagaunts this way with the likelihood of 5 or possibly 6. I also have scoring Tervigons which are no joke. Given the the game is now largely objective based, this is a lot of troops to be dealing with.
6) Although they are not monstrous creatures, I have 9 Zoanthropes which are also pretty resiliant. I can see a place to swap one of these groups out with Hive Guards, which are like mini monstrous creatures. I do have 7 entries that are genuinely described as monstrous creatures.
Only issue with this list, is there isn't currently an official model for the Harpy. I have heard lots of rumours of one coming out, but until it shows, I've got a LOT of Termagaunts to paint.
Looking at other Montrous creatures, what I am obviously missing is Trygons. My biggest issue with these guys, is that when they come in you know they are going to get shot to pieces and it is almost impossible to get cover saves for them. Of course, the rest of the army is then safe for a turn, but I have the Carnifex models already and they will be good close combat support for the Zoanthropes if needed and the Brain Leach Devourers are an excellent stand alone weapon. I may also be using Termagaunt Screens to avoid close combat, because depite this being Tyranids, this is not a strong Close Combat Army.
Don't know if you can use any of these ideas, would like some feed back on this too