The Woods are Lovely, Dark and Deepby
pmichaudComment: Welcome from the Critique Club!
Composition:
A little flat. I'd be curious what focal length was used here. With a wider shot it would give a more expansive feeling to this. Another approach would be to try to think in terms of layers for this type of shot. Get something in the foreground, mid-ground, and background to create depth. If you were to reposition the camera to create a visual line through the shot, either with the path or using the trees it would stronger as well.
From your description you mention that the trail keeps going up. Why not incorporate that feeling into the picture by getting a shot where the trail goes up a lot?
Exposure:
Tough lighting to shoot for. Quick, easiest and safest bet is to expose for the trees. Aiming for an area of trees with more consistent lighting would help as well. Generally with trees you underexpose by about -2/3 of a stop because vegetation tends to be fairly reflective. A circular polarizer of a graduated ND filter would also help get the sky exposed correctly while allowing you to expose the trees properly.
Color: Overall I'd say its pretty good. The colors are rich and well saturated with a fair bit of variety. (yes there's lots of green but lots of variations on green)
The challenge: For this challenge, Waldo is best to be in plain view but blended into the background. I like that you didn't place Waldo too far back in the scene however hiding him behind a tree just doesn't work for me. To be honest I wouldn't worry about that too much though. For this challenge a lot of shots included people in ways you would never want to do and would likely compose for or photoshop out after the fact.