Playroom in the making

We live in a modest three bedroom plus loft, two story with a partial basement. The basement is unfinished. The three bedroom were once our master, a guest room, and my craft room, with our office in the loft Once J and I decided to have P, the guest room became her room, my crafts got a new fabulous home:

and were moved to the office. The craft room became the guest room. And we talked of making the basement a playroom. Now that she is here and her toys are about to multiply and are growing, we have talked about this a little more.

Since we are not handy and we don't have the budget to really do what we would like to the basement and we rarely have overnight guests, we are going to make the guest room our playroom! I am really excited because we are going to reprint too!

I already have some ideas for storage. Like this:


And I want to put something on the wall like this:


Now, what color for the walls? I know that some of the storage bins will be pink and green (like in the picture), so I start there but I need a third color. Purple? Gray? Something else? Help!