Thanks for the nice comment. These two images are renders using Terragen 2. Renders like this at 1024X1024 take me (on my old 2-core computer) about 2 hours. Converted to jpg for a skybox, they are the same as any jpg image regarding resources I imagine. You will have to ask the mapper experts about this to be sure.
BTW, I sent a full set of renders to JohnnyE this weekend for the skybox. If anyone else wants them, let me have an email and I will send them over.