Our level editor has a total of 5 texture-layers, but this number is somewhat arbitrary -- everything gets baked down into a single texture map in the end. Since we haven't experimented with texture-blending (yet!), all of our upper-layer textures contain transparencies and are stored in .tga format to avoid mipmapping/alpha-channel issues.
Below is an example of some extra details added to the grass via a secondary top layer containing a few flourishes:
It's subtle, but further helps to break up the grass.
Once this basic layering was in, it was time to create various aesthetic extras. However, to get the most mileage out of our decorations, we decided to reuse and expand on our roof-tile-rotation feature by allowing any texture to be rotated (0, 90, 180, or 270 degrees) and mirrored (horizontally and/or vertically). While such drastic transformations usually result in obvious seams, none of our decorative tiles touched tile-edges or were big enough to look odd following random transformations. Below is an example of a single leaf tile placed as is, and then randomly rotated/mirrored.
These random transformations were actually done by hand, though, so our next step was to create the concept of tile "mini-sets" that would automate some of the work for us. Each mini-set consists of 1-n amount of tiles, and a list of valid transformations for the mini-set as a whole. The editor allows for filling/painting with mini-sets just like with regular tiles, except the actual tile placed on the map is randomly selected from the list and transformed according to specifications.
Mini-sets require a bit more groundwork to set up, but they've already proven big time-savers. Below is an animation of cycling through some of fill possibilities using a leaves-set.
With more experience, it quickly became evident that it was beneficial for virtually all decorative tiles to be part of a mini-set. With paths, for example, we split the stone pieces into centre/corner/side mini-sets and painted with them directly.
Next up, we'll try to make that building look a bit less like a stone slab.