Julie,
I have 4 grandsons (ages 1-9) and one little granddaughter. I've made them all 'little' quilts for using in front of the television for for curling up with when reading a book with grandma. :wink:
For two of the boys I bought fish fabric, for another grandson the fabric was a jungle print with lots and lots of animals and leaves and the other grandson got monkeys. I used colors from the focus fabrics and just did a simple nine patches and alternated them with blocks of the focus fabrics. Then I bought the wildest fabrics I could find to put on the backs of the quilts. The quilts were bright and cheery and are well loved!
Some magazine, I can't remember which one now, had patterns for trucks to piece. They made a cute quilt. Hmm. Which magazine were they in? I'll look but I think they got tossed during a recent cleaning frenzy here. I don't know if this helps at all or not. I still want to make the bug jars for one of those boys. Have you thought of having your grandson draw a picture of some trucks and incorporating the drawings into the quilt? There are a lot of possibilities out there. Design your own trucks. After all a truck is just a rectangle with some circles for wheels. Add another square up front for the cab. Keep looking and don't give up.
Check out the children's coloring book too.
http://209.200.122.122/detail.cfm?pid=5636&CFID=19984&CFTOKEN=43724505
Check the above out. Truck pattern. I knew I'd seen it somewhere. Enjoy!