This means if it is image you also do not get a thumb nail view and also do not have the option to use the light box to view the images.
A mod I would like to see is the ability to re use the attach BB code and have a thumbnail preview with the light box option.
Jake has posted more information in this thread stating why it is not possible due to permissions -
I would pay for a mod like this personally as it would mean a start to being able to reuse attachments in Xenforo with out of the box settings which is currently lacking in the core.
Not being able to reuse attachments properly also means people are more likely to reload attachments which increases the cost of storage for server admins which can be at a premium in some cases.