Tips and tricks for avoiding repetition in CryEngine landscapes

By no means should you have to do all of these. Just pick and choose from this list to make your level look more realistic. - Smother the landscape with vegetation (ensure random rotation and random size are ticked in the vegetation options).
- Ensure you control where vegetation objects can be placed by setting the maximum and minimum angles of land they can be placed on, as well as what elevation they can appear on.
- Put a 100% opacity material as a "base" for your landscape, then draw over it with low-opacity materials until you end up with a mottled colour. The aim is to avoid having a landscape that has large areas that look exactly the same colour.
- Avoid overly vibrant colours everywhere (ie, high saturation); repetition shows up more easily in things that have high saturation since it ramps up contrast a bit.
- Use several different vegetation groups (eg, one that's got lots of small bushes, one that's got grasses, one that's got dense trees, one that's got rocks... then use these in different parts of the level to make a mixture of plains, forests, clearings, valleys, shorelines, etc)
- Fiddle with fog and lighting settings to change how far you can see
- Add details to your landscape so your screenshots don't have any blank landscape in it. When you're taking screenshots, look at everything that's on screen and make sure it looks realistic by touching up your level before committing to the screenshot.
- Add roads.
- Add rivers (they can only go horizontal, so if you want one going down a hill, you need to break it into horizontal runs joined by waterfalls (ie, water particle effects / waterfall-shaped meshes with the waterfall material applied to it).
- Add decals (google "CryEngine decal tutorial") to break up repeating textures in places where the player will be walking around (eg paths, areas around your architecture).
- Carefully manually place a few important features (eg a big tree or rock or whatever) as Geometric Entities, so they can be an interesting unique part of your landscape. Consider framing your views to look onto features like this.
This is by no means an exhaustive list. Experiment with other stuff outside of this and you can get something pretty cool.