This is a well-painted example from CoolMiniOrNot. To make something like this, out of old 40k bits of course, I had to think about it a bit. I took some inspiration from examples on Tactical Wargames forum and came up with the following.
This is made from various guardian, dire avenger, and wraithguard bits. I tried to maintain a similar build and style to the metal epic version, with a bit of action to the model.
Another shot from the front.
The side and back, showing the back fins and the jump jet.
This is a size comparison with a first generation epic phantom titan. It's a bit shorter than the metal epic revenant, and is up to around half the height of the phantom to the head.
I have several more on the work table with my available bits, so this can probably form of the basis of an Eldar titan army?
This does show though that my attention span is quite poor, and I really need to concentrate on finishing something before taking on other projects.