My issue is not a lack of good textures, but applying them correctly. Also, the image there is an OpenGL view, not a real render. It'll look alot more realistic when finished.
Which isn't to say I'm not always looking for new sources for textures, so any links would be welcome.
I use CGTextures.com - they are free for 15Mb but if you use a lot of them then you can sign up for membership which is not all that expensive and you can download much more.
Have you seen the 3DMark demos ? I cant remember exactly which one but I think its 3DMark06 which has a similar 3D steam punk airship animation.
OpenGL is capable of really high quality renders but most of the time its used in its basic form for preview modes. If you want to go one stage higher and keep the speed up then try out Gelato from nVidia. You will need something as an editor that is Gelato capable tho. If you want Pixar quality then your looking at PR RenderMan tho...
Good start - looking forward to seeing how it progresses...