With a number of people, including our own Whitehorn and King Fluff, building their own 40K scale Titans I've come to realise that there seems to be a lack of ready available reference pictures of older Titan classes in both Epic size and other 40K size.
I think this needs remedying, and I'll get the ball rolling.
These first are from
Collecting Citadel Miniatures.
Prototype Knight Paladin by Epicast. 40K size.

It appears as though Epicast were also working on Crusader and Errant class as well.
Reaver Titan by Armorcast. 40K size.

This design is based on one produced by another comapny called Biasi Studios.
Warhound Titan by Armorcast. 40K size.

This to is based on a design produced by Biasi Studios.
Armorcast Titan weapons, 1. 40K size.

And 2. 40K size.

An Armorcast unreleased Titan head:

40K size.
And their infamous Imperator Titan prototype:

40K size.
Reaver Iron Armour head by Merlyn. 40K size.

Also for a Reaver, the Laughing God head by Merlyn. 40K size.

And a final head from Merlyn, a Reaver Skull. 40K size.