This is addressing the much earlier question about interior photos: Patrick Beaver's THE BIG SHIP (1969, reprinted 1987) is a pictorial history of the Great Eastern and a great source for photos of all aspects of the ship. The picture reproduction is pretty good.
On the subject of "Leviathan." If one can find a copy, and it isn't all that hard to do, the January 16, 1858 Illustrated London News has, as a centerfold, pages 56/7, a lavish colored image of the "Leviathan", surrounded by likenesses of 16 prior ships tracing the development of the English steamship, also in color. Amongst which are the Great Western and the Great Britain. I've seen the centerfold, removed from the paper, priced at about $175 (still about $2500 downstream of what a similar Endicott or Currier litho would sell for) but one can often find the whole paper for a third of that.