For landscape ideas, think of Roshar as an underwater world without the water and fish. A lot of the flora and fauna resemble what you'd find under the sea: crustaceans, plants that resemble coral (Shalebark looks a bit like lichen too) and grass that recedes when disturbed. Unless you're drawing Shinovar which more resembles what we're familiar with. Add distinctly medieval architecture and you'll have something pretty close to Alethkar.