Don't know if you are familiar with the Mr. Men series. I think it is more popular in England than here, but I have a friend who is an English transplant who painted Mr. Men on his baby boy's nursery walls. I suggest this one because they are pretty simple figures. Lots of tracing large circles, straight lines, etc., and coloring them. Much simpler than Dr. Seuss for example. Mr. Cheerful and Mr. Bounce, below, might be a good place to start.
There are many great ideas for a baby boy room. The one thing I suggest is going with a color and furniture scheme that will easily go from baby to toddler and maybe into childhood. For example, instead of light baby blue walls, go with a shade of denim. You can try Googling images of baby boy rooms and go with what feels right.
There are many rooms here that members have done see this posting for some great ideas.
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