Cry for help in the Guest Room

This weekend, we started clearing out the old office to make way for it to become our nursery, which I'm thrilled about and can't wait to see come to life! The down side is that this means we had to shove all of our office things into the guest bedroom. We got rid of some things and decided to put a few more in storage, but there's a lot that we wanted/needed to keep out. This leaves me with a dilemma.

 Steven has a decent collection of police memorabilia (police cars of all sizes, badges, police stuffed animals, etc). These are important to him because his dad and brother were/are in the line of duty, and he works in a similar role. I want him to be able to display his things, but I don't want it to look tacky.
Right now, things are just piled all over the room. We do have PLENTY of wall space, and I know this would be the best way of going about solving the problem. I just need ideas. Oh, and they need to be inexpensive because all of our money is going to baby right now. Please help!!

 Some of his things piled on the nightstand.

 Our bookshelf cluttered with random knick-knacks.

The bed (I would love to buy a new comforter, probably blue, that would fit better with the room) and all the wall space above it

Desk (I will accept ideas/recommendations for painting it)...and the books stacked between the desk and bookshelf do have a home. We just have to paint the new bookshelf they're going on in the living room. 

Dresser with more clutter on top and nothing above it.