I would pick a color scheme you really like and just find things in those colors. You can mix and match patterns in the colors you choose, which is really popular now. I agree, look on Pinterest for some ideas. You can always incorporate animals or birds also, but make it an accent, not the actual theme, because it is easy to go overboard on a theme.
There are a lot of owl things out there...
For me neutral is really based on the colors you choose. Most animal decor is neutral since it is an animal.. Besides maybe butterflies etc. But good colors could be silver white and yellow or many more.... There are so many options. Pinterest neutral baby rooms or unisex baby room ideas etc... You'll get tons of great ideas
I'm a very outdoorsy person and love nature so anything along the lines of that would appeal to me except camo. I'm not a hunter and feel like camo is over played