Finally painted my Eoraptor model and discovered Terragen lol
HOW I DID THIS
Model made and painted in Sculptris.
Terrain made using Terragen and rendered, saved as bitmap, resaved as JPEG in photoshop.
Background brought into sculptris as BG to Paint mode.
Exported from Sculptris as a PSD
Brought the bg BACK into the PSD and did some lighting tweaking (shadow, lighting on model, reflection of model in the water, screenshotification)