Thanks for the kind words regarding MLA and for your question.
As you may have discovered, you can replace the default WordPress file icons with a more attractive set by navigating to the Settings/Media Library Assistant Uploads tab. The current MLA version does not have any features to replace these icons with a complete set of your own.
MLA also lets you substitute a “Featured Image” for the icon displayed for a non-image Media Library item; this is on an item-by-item basis.
If you can give me more information about your goal I can give you more specific guidance or investigate the work required to support your goal. Thanks for any additional details you can provide and for your interest in the plugin.
It has been three months since my last post in this topic. I assume you have found a suitable answer to your question.
I am marking this topic resolved, but please update it if you still have problems or further questions regarding icons for the file types.