Changing story production to do the inspired one

[The Rock Worm]

Get a 3d modelling program. Learn it. Get good at it. Get to work.
Get Gimp/Photoshop, and learn to use it mixed in with getting good photographs.

Not going to let you down easy here. Nobody is going to make that Shoggoth thing for you. If it's so vital, you'll have to make it yourself. Unless, of course, you contract a freelance artist and pay him. But that would be silly as the custom story would be free.

Good luck on it, though.

I know the Shoggoth would be difficult. One idea is 're-skin' and /or 're-model' the worm from Penumbra enough to be a Shoggoth.

If I did make a texture(s), how do I add it as a readable one for Amnesia? Haven't tried so not sure.

What about the coding to make it attack even other monsters?