If you are working with a registered version of Terragen try rendering at 4000x3000 and using a good size terrain eg 1024 as a starting point and using Ifranview to resize and sharpen and Photoshop for everything else.If unregistered render at least 1024 x 768 (you can go a little higher), and 513 terrain size. Make sure that your detail slider is all the way to the right and you have at least fast sub pixel smoothing selected in the render settings dialogue.

It's not bad. Just try working more with surface and atmosphere colors. Also, try bring the gamma setting down to below 1.5

Thank you for you comments with all my Terragen Images I try to get as close to natural as possible. I offten get up out of my seat when i'm working and stand back form the computer and ask my self "Dose this look natural"? The bear patchs in the surface map (In the forground grass area) is rock and as such te grass dose not grow there. As for gamma I don't like having gamma to low as it makes the image kind of dark, also for my skyes when i'm adjusting the settings all I need to do to see if I'm doing it right is look out my window. I come from a photographic background (Shooter since age Six) so I know light, the kind of dark blue sky you get with adjusting gamma you find at high altitudes like base camp 3 on Mt Everest, if the sky here seems to bright or to dark please cheek the calibration of you monitor.