Show Thumbnails for non-image Attachments

Haven’t tried EG-Attachments, but Attachment Manager works perfectly fine for me.

I’m not exactly certain what you’re wanting these plugins to do. They don’t give a thumbnail of your *actual* document, they just give an icon representing the *type* of document. That is all that they claim to do.

See the screenshots for EG-Attachments here. The Attachment Manager plugin has less options, and its output looks very similar to the first image on that page.