I was recently commissioned to sculpt and cast some custom marine heads, torsos and helmet plumes.
The commission consists of standard helmets, some with plumes, and a heavier helmet for sergeants.
The client specified he wanted a more aggressive, snarling look than standard marines (and originally wanted to use modified
FW Khorne Berzerker heads).
As this is a build-only commission (not construction of one-off completed miniatures), we can't recast
GW parts, modified or not, so the sculpt was necessary. All sculpt here is from scratch.
Here's my take on it. The plume is a separate part (and fits standard marine helmets too). The helmet is upscaled very slighlty (taller, but not so long to allow the plume to fit easier in front of backpacks). The sergeant's helmet will have a barbutte style 'over helmet' and will be a modification of this one. Again, the plume will be a separate part.
As I'd like to be able to retail the helmets when they're done, I may try to move it a little further from standard Space Marine design, possibly by flaring out the bottom (where the cheek pipes are) in a more Star Wars Stormtrooper / Clone trooper style.