I think the outside walls can be parged with mortar and finished just about anyway you like... Broom swirls, spongy popcorn, fake stone or brick is easy with a pointing tool... The main thing is to be ready to do it after the parge just is beginning to set up... And, of course, it can be painted/dyed...

Ask yer concrete guy about it... Of course, the wall will have to have parge up to the the fill line...

But then again, I have never done an ICF foundation so I'm kinda uswing what I know about standard footer/block building...

B~