Here's a simple method I found to make terrain tiling less obvious without using a lot of resources. It's very straightforward, but someone might find it helpful - I tried some more complicated methods before realising this works.
For the terrain, I used six different frames of noise and assigned them at random.
For the grass, similar but with drawn frames instead of noise.
Left click to turn off randomness, right click to turn back on and re-roll.
Later on, I will make stuff like grass re-roll if two identical images are adjacent - when that happens, it looks strange.