Uhm....... That is more Eldar on top of a dreadnought than a terminator but it looks good nonetheless ; just size comparison is weird...... Except it would be a terminator statue of course, then it could be made awesome.
Depending on what you read Eldar are taller than humans but just a little smaller than a space marine according to what is out there for a size comparison but there is so little about the sizes other than space marines out there that who knows. However if that was the size of an Eldar compared to a space marine they should just turn their bolters on themselves and ask forgiveness from the emperor for losing at all to Eldar.
Perhaps a fraction large, but it could be a Dreadnought? Anyhow the concept is great And the Mandrake that I've just seen pop in above me there is so atmospheric!
That's a beatiful mandrake picture I commissioned from a russian artist. Search "Inkary" on DA, she charges absolutely nothing for the amount of her skill. @Jorimel Probably, I never tried that and I don't know if it's possible with plasticine. Requires investigating.
I've used silicone moulding medium (the kind you pour rather than knead) to good effect but I'd say watch for bubbles. It is flexible around undercuts, but I wouldn't be completely sure your model would be 100% undamaged in removing it (more bending than anything). I've cast simple shapes in resin so far, but it does pick up detail. Cheers, I'll go and look up Inkary now!
As a sign of me getting back into shape, have some more artwork. I'm not sure how I feel about the Seer on the left. The design of the helmet (mainly the insect-like things hanging from it) is quite odd. Ah well, I'm sure someone might know how to appreciate it better than I do!