Since you can query for attachments you could create your own VF page that gives you some 'report' like features on the attachment object. Your controller could query for attachments that meet your criteria
list<Attachment> attachs = [Select Id, Name, OwnerId, ParentId, ContentType From Attachment];
The main issue is if you want to use the attachment body. There are a few issues with this. you can't query for the body of an attachment if you are retrieving multiple attachments. From the documentation
You can access all of the fields using a query() call. However, you
can't receive the Body field for multiple records in a single query()
call. If your query returns the Body field, your client application
must ensure that only one row with one Attachment is returned;
otherwise, an error occurs. A more effective approach is to return IDs
(but not Attachment records in the Body field) from a query() call and
then pass them into retrieve() calls that return the Body field.
The other issue is even if you use the retrieve() call to get the body it is encoded in base64, so you have to go through quite a bit of effort to decode the body data. it's doable, but not pretty.
So basically,m if you just want to report on basic metrics around attachments, like number, ContentType, Owners, and Size, then you could do this with a VF page by querying the Attachments records in your controller.
If you want to use the Body of the attachment, you have to get into decoding the Base64. Not impossible by any means, just a bit more complicated than a simple SOQL query with some VF.