Decorating ideas - help me out??

I had the embarrassing realization this weekend that we have now lived in our new house for 7 months (!!) and we have not decorated a thing. Well, we did paint one wall of the living room and hang some pictures upstairs, but that's it. I feel kind of bad because at our old house, J's room was decorated from top to bottom. I spent so much time on that room! I had several prints of baby jungle animals that I ordered from an art website 5 months before he was born, and those were my "inspiration" pieces. The walls were painted -- I'm talking horizontal stripes and hand-stencilling. The rug, bedding, and artwork all coordinated well. I even busted out my sewing machine and made a cover-up for a little niche in the wall, complete with velcro tabs and piping.

J's new room? Sad. Just pitiful. Plain white walls, plain baby furniture which is looking more and more babyish the older he gets, no pictures on the walls, no curtains, etc. So my next project is to decorate J's room. Our new house has 3 bedrooms, and right now the 3rd bedroom is the playroom. However because it is the bigger room, we'd like to turn the playroom into J's "Big Boy" bedroom, with new furniture, and some type of decorative theme. It only seems fair that if (when) we have another kid J should get the bigger room, you know with seniority and everything.

So here's what I want: A more grown-up room but I don't want it to look like a teenager lives there. I like color within reason (i.e. primary colors = ok on the bedding, not so much on the walls). The furniture will likely be medium-toned wood such as oak, maybe a little darker. I like coordinating stuff but not "matchy-matchy." Not counting furniture I'd say our budget is about $300. I'm willing and able to paint, put up chair-rails, etc.

I'm not going to post a picture of the room as it is until I have a good before and after; there's not really anything to look at. Neutral carpet. Off-white walls. Hideous vertical blinds. Heinous plain white sliding closet doors (I may replace these with folding doors). Just big enough for a twin bed, a dresser, a desk, and some type of storage.

Here's some bedding I like, mostly it's the colors. I think we're leaning towards a dinosaur theme. Any ideas? Anyone? Anyone? Bueller? (by ideas I mean maybe a pic of your own kids room, ideas on wall or window treatments, or point me towards a good website or store that has good quality but affordable stuff...).