Hello Askalice -
If you wish to prevent the gallery from being added to new listings, you just need to make a change to your account preferences. From the My Account menu, select 'Acct. Preferences' and in the Listing Enhancements section set the option for the Scrolling Gallery to No and then, a bit lower down on the page, click the 'Update account preferences' button to save that change to your account.
If you wish to have the gallery removed from already active listings, please file a support case from under the Help tab of the site and we can run a command that will remove the gallery from active listings that are eligible for revision on eBay.