Unitree will include a Texture splatting heightmap renderer. Essentially multiple tiling textures are blended using some alpha maps which you can paint in Unity.
We want to ship a bunch of tiling splat textures with which users can paint their terrain. While it's possible to just take a picture of the ground, remove the lighting and be done with it, it's not going to look great. Making it look really good, takes a bit more effort.
- The texture should not have low frequency detail, but lots of high frequency detail. The goal is that if you zoom out and look at the texture tiling many times over, you should not be able to detect that it is tiling. Here is a great article describing how to do that: 
- The texture should tile perfectly, with no visible seams at the edges.
- The texture should be laid out so that one tile covers a 3 - 10 meter area. The resolution should be around 1024*1024 resolution. This gives you a 3mm to 1cm area per pixel. This should be enough to have small flowers and grass detail in the texture.
Requirements: Texture must be supplied in .psd or tga format. Texture must be power of two.
Work in progress
Add zipped textures of splatmaps you are working on here: TheSplatMaps