After the buzz my new shelves caused, I decided to search for projects to share with you. I found this video where a guy build a very nice shelf which, unlike mine, can accomodate bigger models
I also found this post on a blog called "Ikea hackers" with ideas for building shelves:
This other one in the official Hot Wheels Collectors website
And, finally, a how to on eHow
Hope this sparks your DIY spirit!