Their home page says:
If you would like to add something to the database, click the "Submit Changes" link displayed with each machine and then follow the instructions. We encourage everyone to share their photos, files and other pin-related information with others in the hobby; all submitted images should show these machines in their original factory condition, unmodified and unrepainted. The database is an unparalleled resource for all pinball enthusiasts, with the largest collection of pinball machines available online, but its success depends on its users. For more information on the IPDB, click the links at the bottom of the page.

When you go to the entry for a particular game, the first line has the basic information, with the "Submit Changes" link way over to the right, like this:
Jungle Life / IPD No. 1337 / December, 1972 / 1 Player [ Submit Changes ]
For any game, there are about 12 distinct views that they want, plus additional interior views for electromechanical games. Images of associated paperwork are also welcome. The page for submitting pages will help you think of items to submit.
.................David Marston