I have painted up several heads for my Lord Commander Eidolon. i've shown them below.
1) Sternguard head
2) Sanguinary Guard head:
3) Homemade Helmet:
I like my homemade helmet, but sadly it can only fit in one position because of the jumppack! Not very safe with that plume being so close to the air intakes!!
A very nice guy from the US on the Bolter and Chainsword forum has sent me a pack full of Space Marine heads. So I will see what else shows up!