The last plan I heard was to use photos of the miniatures so that they were instantly recognisable, but the designs aren't finalised yet.
There are other options including using art, or using art for the veteran versions and photos for the normal ones to make them easily distinguishable at a glance.
I expect that more designs will be uploaded as we go through the KS and get more of the graphics done.
Personally I would be happy with either art or photographs as I don't think they'd be any more difficult to distinguish if they were the former but I would not like them to be mixed between art and photographs as I like consistency! That's just my two cents though if it counts for anything!