In looking at this, here is the query that I have found should give you what you are looking for. This query was run against the SMART_REPOSITORY_LOGICAL_FILE table within the project. The SRLF_NAME field has the filename in the following format... __Filename

SELECT [SRLF_ID]
,[SRLF_PARENT_PATH]
,[SRLF_NAME]
,[SRLF_PHYSICAL_ID]
,[SRLF_IS_DIRECTORY]
,[SRLF_LAST_MODIFIED]
,[SRLF_SIZE]
FROM [default_demo_db].[td].[SMART_REPOSITORY_LOGICAL_FILE]
where SRLF_PARENT_PATH LIKE '.attach%' AND NOT SRLF_IS_DIRECTORY = 'Y'
order by SRLF_NAME
In researching and testing this I also found that some of these attachments show up under History and Baselines. If you would like to see those entries you could use the following query.

SELECT [SRLF_ID]
,[SRLF_PARENT_PATH]
,[SRLF_NAME]
,[SRLF_PHYSICAL_ID]
,[SRLF_IS_DIRECTORY]
,[SRLF_LAST_MODIFIED]
,[SRLF_SIZE]
FROM [default_demo_db].[td].[SMART_REPOSITORY_LOGICAL_FILE]
where (SRLF_PARENT_PATH LIKE '.attach%'OR SRLF_PARENT_PATH LIKE '.baseline%' OR SRLF_PARENT_PATH LIKE '.hist%') AND NOT SRLF_IS_DIRECTORY = 'Y'
order by SRLF_NAME
For more information on this table use the link below...

http://alm-help.saas.hpe.com/en/12.53/api_refs/project_db/topic530.html