Hello Bradon,
Thank you for your message.
New catagories would have to be suggested to me for consideration as there is no "Suggest a Category" utility on the website.
As for aircraft underbellies, belly shots are less than ideal and the vast majority of such shots that are uploaded to the site are rejected.
The reason for this is that straight-on belly views are less than ideal. It's like taking the photo of the back end of a dog or cat. It is not a complementary view.
By contract, views from the top looking down on aircraft are extremely rare and are thus very impressive.
Cheers,
Henry Tenby, webmaster
www.AirlineFan.com