Bigger Sharepoiunt slide library thumbnail SOLVED !!!

This worked for me to get a better thumbnail

Note that the solution relies on having a naming convention for your files which you apply after you have loaded them up to the slide library eg ENG_02_0010, ENG_02_0020 rather than leaving them named as is when uploaded to Sharepoint.

1.Create another field called Preview say and make it a picture (format url as picture)
2. For each uploaded slide put the url link as http://siteName/slidelibraryName/_t/ENG_02_0010_pptx.jpg (same name as your slide with a _pptx.jpg extension)
3. Get rid of the standard thumbnail from your view and put this new column next to the selection box

Worked for me , much bigger and readable thumbnail !!!

PS
In SP designer you can find all the jpg thumbnails in the _t directory under the slide library