You shouldn't have any problems if you stick to low light plants. If you want to use "higher" light requiring plants definitely place them in the middle where most of the light is! Marimo balls are awesome, they're tricky to incorporate into an aquascape though. Again, depends what look you're going for. My shrimp love crawling around and cleaning them. You just have to gently squeeze them and turn them over once in a while to make sure the other sides of the ball are getting some light. Mosses in general are a good option.
Some fish are timid and like to hide among plants and/or rocks, this helps them avoid stress and make them feel like they're in their natural habitat. Keep this in mind when choosing your plants and fish