Step 1: Sketchup
You can download the sketchup file here. You need the Google Sketchup program (free version is enough) to open it.
Step 2: Cutlist diagram
Step 3: Making the engine head
Step 4: Making the rooftop
I also used the router to cut a 1/4" groove along the inside of the arcs and the side rail so that the roof board can fit in.
Step 5: Bed body
Do not throw away the 2 cut-off pieces from the window - they are used as the 2 shoulders for the toy chest.
Step 6: Toybox
Step 7: Headboard
Step 8: Thomas face
Step 9: Paint & assembly
Step 10: Finished
Here's the finished bed. The train engine head was fixed to the toy chest with hinges and safety lid support, giving safe access to the back of the toy chest. If you want to go nuts, cut some openings on the side of the bed and add some drawers, or better yet, train wheel shaped drawers :D
The project took me more time than I expected, about 3/4 of the time was actually spent on the design and sketchup, but it's been fun for me and the big smile on my son's face makes it all worth it.