Google Sketchup. This will involve lots of creativity, but also patience and accuracy! Sketchup is a free programme that can be used to design very simple objects all the way up to huge skyscrapers! If you can, dowload the software at home (ask parents first!) and have a play - see what you can discover!
Here's a quick preview of the sort of thing I hope we can produce (I know yours will be much, much better!):