Well spotted Amit. You are actually correct, the wheels depicted on the website are obviously too large for those wheel arches, such that they wouldn't be able to turn without hitting the fender wall, and would crash into the body when going over bumps!
Tata nano website T&C: Tata Nano :: Terms & Conditions
Point 7 says: "While Tata Motors Limited has taken care in the preparation of the contents of this Website, this Website and the information, names, images, pictures, logos, icons regarding or relating to Tata Motors Limited and/or its corporate parents, subsidiaries, affiliates etc. or the products and services of the same , are provided on an "as is" basis without any representation or endorsement being made and without any warranty of any kind, whether express or implied, including by not limited to, any implied warranties of satisfactory quality, fitness for a particular purpose, non-infringement, compatibility, security and accuracy. To the extent permitted by law, all such terms and warranties are hereby excluded. In no event will Tata Motors Limited or any of its corporate parents, subsidiaries, affiliates etc. be liable (whether in contract or tort (including negligence or breach of statutory duty) or otherwise) for any losses sustained and arising out of or in connection with use of this Website including, without limitation, loss of profits, loss of data or loss of goodwill (in all these cases whether direct or indirect) nor any indirect, economic, consequential or special loss."
I just find it rather pathetic that Tata is still trying to deny the lie by saying that wheel covers can somehow affect the width of the tyre!