Hi Mark, Glad to see you're still around. :)
You have a few choices, all can be found here:
Johhno Uk's scenery is what is used in the ETO install and is what most people are using these days. Then there's Winding mans scenery manager which also improves the weather, seasons and missions. It's installation is a little more complicated than Johnnos.
Von Oben also did a mod for the Winding man package which uses Johnnos textures as a base, this is really very good.