I've always loved the Smarties Rug designed by Suzanne Sharp for The Rug Company. It has been featured in many design publications in children's room designs (including in the book Room for Children by Susanna Salk). Yes it is expensive for a child's room but if you can keep your kid from eating in their room and generally take your shoes off when you enter your home, you will be fine! Arts and crafts are for a playroom, kitchen or outside...not the bedroom.
The depth of the colors in this rug is fabulous and modernly simplistic. It is a Nepalese rug made by hand with Tibetan Wool. Smarties comes in a large scale of standard sizes and can also be custom sized to order. Prices are $2000+ depending on size.
Now for the low. I received the Company Kids catalog today and opened up the rugs section and saw a similar design. Theirs is called the Big Dots rug available in an orange/olive combination as well as a red/blue combination for boys and some pastels for girls. Prices range from $90 for the 3x5 and $290 for the 5x8. The quality will not be the same but if the size and colors work, give it a shot.