Removing the 'X' icon images from service offerings is not working in release 14.1 Catalog product but the same can be done in release 12.9 product.
CA Service Catalog 14.1
If you have an image against an offering and you delete that image of file, you're going to get a broken link 'X' image.
This was introduced in 14.1 version probably for a uniformity across the board for all the offerings and to differentiate with the 'Browse Catalog: Show Folder Icon: Yes / No' feature
Note: This feature when validated on 12.9 version, there is no 'X' icon (broken link) present next to an offerings even after adding or removing.