Excellent work! I particularly love the smaller stuff, inspiringly done. The bigger ones still look a bit much like a recognisable 40k ork dread plonked down in an epic game though (perhaps add more smaller detail? Panel lines, plating, various little details?)
I'd suggest basing the Super-Stompa on a 50mm round base if you get hold of one - it makes it more obvious to the opponent what it is compared to the Stompas. I'd suggest maybe 70-90mm round for the Great Gargant then too.
Don't worry about the Stompas being too big - they look a good size and appropriate for a 4+ Reinforced Armour vehicle. Some of the epic older models were out of scale with the infantry - the old planes and titans in particular- and a lot of people these days model their vehicles bigger so that everything looks is in scale with each other, sometimes referred to as 'truescale'. This is a game where the
first official Thunderhawk model was around 3cm long and the most recent official
FW Thunderhawk was 10cm long (both are on the same size flying stand in those two photos) and both are completely game legal so there's a fair bit of leeway as to model size. So long as it's pointed out the opponent what is what at the start and types of unit are easily distinguishable all is good.
The "universe" of 6mm Sci-fi available continues to grow ... 
